As light as possible, with the exception that I always take my camera gear. For weekends I fit everything in a small backpack that easily fits Ryanairs carry-on limits, for longer holidays one large checked backpack. For a hiking trip the large backpack has to hold a tent, sleeping bag, food for several days, and that does usually mean washing clothes in rivers on the way. Having to carry all you bring for several days/weeks while walking all day in mountainous regions is a very easy way to learn to pack light...

Light and getting lighter. Excluding sporting or camera gear (hard to travel light and avoid checking if you're a diver or a professional/serious amateur photographer--I'm neither but do one or two golf trips per year) and understanding that the need to accommodate wild swings in weather will limit the ability to pack lightly, I generally carry everything, including computer/electronics gear, in two bags, neither of which is larger than 1500 cubic inches or 36 linear inches--in other words, I'm carrying two personal items as those are generally understood.

I'm in the middle of a week-long trip to Orlando that began with my doing some work outside the office at a location a couple of hours towards Orlando by interstate. That meant I needed to wear a sports jacket, tie, and dress pants. I packed two more pairs of pants, four golf shirts, a pair of shoes that contrast with the shoes I wore to work the day I left, four pairs of socks, two pairs of underwear (one cotton, one synthetic, odor resistant, and quick drying), a merino wool sweater and a cotton pullover sweater (just in case of a chilly night or two in Orlando in the middle of winter--which happened Thursday when the temperatures dropped from the 80s into the 30s that night). A small toiletry bag--essentially a 3-1-1 bag with a 2 oz. bottle of shampoo, a folding hairbrush, a razor, a toothbrush, toothpaste, deodorant, a small vial of aspirin, another small vial of vitamins and sleep aids, nail clippers, and a couple of bandaids. All of this fit in a Red Oxx Extra Small Aviator bag. My work computer, power cord, recharging cords for my work and personal cell phones, and an e-reader (which can use one of the recharging cords from my cell phones) fit into a messenger bag that's about half the size of the Aviator.

It turns out the hotel I'm in has a laundry that I used this morning. This means I won't have to use about half of the stuff I brought down. I've played golf, gone to a restaurant that prefers coats and ties, done some sightseeing in Savannah and Orlando, and gone through temperatures from the 30s to the 80s. I pack the same way for airline trips. My guiding principle in packing: pack for three days and rotate your clothes. No one is going to see you for more than three days--it's only you who will notice you're wearing your clothes again. Add easily washed (and more importantly, dried) underwear and socks with one or two shirts/pants made of technical fabric that can also be easily washed and dried and that may be able to be worn more than a day before cleaning. Finally, trim the toiletry kit--I guarantee you there's stuff in your kit you've never touched.

I'll pack almost exactly this way for a two-week trip to Ireland this summer, except I'll take and check my golf bag, including two pairs of golf shoes, substitute a 23L daypack for the messenger bag, carry my ultralight personal computer for my 15-inch work laptop, drop the blazer and tie, and pack a couple of cashmere sweaters and some rain gear as well as the other items listed above.

I'm planning on taking my laptop bag and a small rucksack next week.
Aiming to have a pair of running shoes, top, shorts, socks + change of underwear, socks, a couple of t-shirts and that's pretty much it.
Maybe a couple of toiletry items.

Going to be in the air for 3 nights out of 6, 2 nights in a hotel and most of the other time sitting around airports / lounges.
Should suffice.

I tend to pack on the heavy side (but then, I prefer car trips to plane trips) and I like to leave room for things (as others said, often foodstuffs) I expect to bring back. I think the "I never check bags; I'm always the first at the taxi stand" mentality can turn into something of a fetish; if it makes you happy, fine, but I don't always feel like schlepping everything through every airport, and am sometimes just as happy to have the airline do the schlepping for me.

I might have missed it, but I don't think anyone's mentioned the issue of arriving at a hotel late at night. (This should perhaps be cross-referenced with the thread on stupid things your company does to save money: insisting that you take a flight that has you getting to the hotel close to midnight the night before something important first thing the next day.) I am a big fan of Rick Steves, and his advice about buying toiletries you need on the way is good as far as it goes (which is to say, for leisure/exploratory travel rather than business travel), but it's not necessarily realistic when you arrive at a hotel after 10 pm, with no shop open nearby (and by the way no place open to eat either) and an important presentation to make at 9 am the next morning.

But, the deal is, you always end up doing some of the schlepping. And when IRROPs occur, the schlepping tends to be a major pain.

Look at both sides. You don't think the "I need to pack everything I might possibly need" isn't a fetish?

I usually pack light. My aim is less than 1 week holiday... no checked luggage. Cold or warm I don't mind. No stress of losing bags, no waiting, and moving around (esp. in public transportation) is way easier.

My personal record was a US-Europe-US flight... I had to go to sort some papers for a couple of days (and I would stay at my parents' house in Europe where I still have clothes), so I just took a small backpack half empty (literally my laptop, mobile/laptop chargers and a clean underwear and T-shirt just in case my flight would be delayed). I even thought about not taking my laptop (and hence not even a backpack) but that would be probably too weird... and it even might led to some questions!

Since I last posted on this thread, I have some thoughts to add.

I went to California for a weekend this summer for a friend's wedding. Thursday to Sunday, summer time clothing, barely even filled my rollerboard halfway. While there, I realized I would be giving my friend and his girlfriend a ride to the wedding (3 hours) so I upgraded my tiny rental car to an SUV so we could all be more comfortable for the 3 hour drive. My friends roll out of their hotel with 5 (!!!!!) gigantic rollerboards, for a Wednesday - Monday trip. They seriously must have brought the kitchen sink. I have no idea what they were hauling around for a relatively short domestic trip. Some people just don't understand "packing light." If I hadn't upgraded the car, all those luggages would've never fit.

Something that makes you realize that you must "pack light" is when you must take public transportation to the airport. We always take the subway + AirTrain to JFK. You have to haul your own luggage up and down stairs so overpacking is a nightmare. We also have no space in our apartment to store any suitcases larger than our 2 carry-on rollerboards. Contrast this to my relatives in the suburbs who have an entire room dedicated to suitcase storage. I'm sure they aren't the pack light kind.

I guess you don't travel to North America much :)

Most of that stuff would wind up in the garbage can at customs...

As little as possible; less luggage means more freedom to move around and explore. When watching people retrieve their luggage in customs I am just mesmerized by the size of some of those things. Same at domestic carousels (my luggage is always carry-on size but I usually check it just so I don’t have to mess it on the plane or during layovers).

Unless it’s someone who is moving to a new country, bringing things to family/taking things home to family I usually assume, probably mistakenly, that’s it’s a relatively inexperienced traveler who will, given a trip or two, see the light.

Oh, I agree on both counts. There's always some schlepping, and thinking you can anticipate and pack for every possible adverse scenario is as unrealistic as thinking there's no need to pack for any of them.

My wife introduced me to backpacking, and that has translated well to traveling light.

I kiss my wife and thank her for being able to travel light when we see those ginormous luggages as we walk past the baggage carousels. One Reddox Skytrain, for a weekend car trip or a 10 day international trip. We also experience extreme amounts of IRROPS flying into SFO, so its easier to get rebooked traveling carry on only.

With proper planning you can get lots of stuff in a canvas 15" tote bag (5 changes of underwear, 3 or 4 shirts, a pair of pants, "toiletries", a pair of shoes), so unless one needs "formal" attire [which for a vacation trip should be enough] one can get by with the 15" tote. If I'm going for 2 weeks, I will take less than a trip of up to 5 days--I'll wash clothing in that case.
So in an absolute emergency:), taking 2 15" totes should cover all bases.
If the overhead bins are filled up, 2 15" totes can fit under the seat in front of you.^
[Before one could print bp's from kiosks or on a home computer, there have been many instances, when I went to the check-in agent and the general question they would ask me "is that all you have?".]

I think a lot of it depends on how fearful the traveller is of doing laundry on the road. Gone for two weeks? Have to pack 14 pairs of underwear, 14 pairs of socks, ten shirts etc... If however you're comfortable with hunting down a laundry now and again on your trip then you don't need all that stuff....

The bathroom sink or tub works for me ;)

I generally prefer trying to seek out a laundry. No matter how much I wring things out they never seem to be dry in the morning.