My company allows laundry to be expensed on trips of one week or longer. However, as in so many other areas, my department has stricter rules: there must be more than five meetings days not including weekends (so a six day meetings, mon-sat, wouldn't count) and you are also limited to $150.

I stopped checking luggage a while back, so I usually travel with about 3-4 days of clothes packed. Almost all of my trips are one week plus weekend travel, so I end up doing laundry on my own dime (as with Internet access, hotel fridge, and many other areas). If possible, I try and find a place close to the hotel to save money.