I have a couple of favorite carry on bags, depending on trip. I have a wheeled Jansport with retractable shoulder straps. It can be pulled or used like a back pack. Its roomy for its size and can hold enough for a 3-4 day business trip. I can usually "survive" on my small baggie of liquids or obtain tolietries at my destination. It has a nice built in laptop sleeve, which is nothing to write home about since most newer bags have this feature. The cool thing is that its located inside the bag which allows more padding when clothes are packed around it.

I also like my eBags Motherlode Mini. It's a bit tougher than the Jansport and the one I typically use on international trips. I have several eBags products and they have held up to some of the notoriously worst baggage handling aiports in the world. The Mini is a great carry on and should reasonably hold anything a person will need during a 3-4 day trip.