At B&Bs or pensions they may offer to do it for you for little or nothing.

Have not tried laundromats - but we don;t go for 3 weeks with a gym bag - more like a 24" checked bag and a carry-on.

I always take enough panties of the trip and do wash out bras - which dry in a couple of hours - in the sink. We pay (yes, through the nose) to have clothes washed in hotels - since in the summer I can't wear things more than once - just too icky/sticky.

We usually rent apartments with laundry facilities or at least a washer, but we have done everything above except the wash-dry-fold.

I don't mind an afternoon in a laundromat with the locals once a week. The laundromats are fairly quiet in the afternoon, and we have done it in England, Paris, and Provence.

Last year I stayed at nice hotels in Dresden, Leipzig, Weimar, and Berlin, for which I paid about $125 to $150 per night for 23 days. I'd spent $200 on Alaska Airlines tickets to get me to Seattle, then about $1500 on plane fare to Frankfurt and probably $100 to $200 on Air Berlin (Can't remember for sure). The cost was well over $5000 for that trip, probably more than $6000.

It finally dawned on me how silly it was to wear pants multiple times until they were unattractively baggy--just because I was too cheap to have the hotel send them out to wherever they have laundry done.

In the future I will avail myself of the hotel's laundry/dry cleaning service. I'm too impatient to spend two or three hours hanging around a laundromat, as I've done in the past, and it seems silly for me to balk at spending a bit extra on laundry after I've spent a small fortune on the trip.

I'll still wash underwear and socks in the sink and hang them in the shower, though.

Some B&B's will have a policy against doing laundry in the room.

We always find places where they will wash/dry/fold. It is much less expensive than having a hotel do your laundry. They are easy to find in sizable towns and cities. We drop off the clothes in the morning and pick up in late afternoon.

I think it's a lot more efficient to just find a place to have your laundry done. I'm not against rinsing a lightweight item out in the hotel sink with shampoo. What makes this work for me is simply not washing clothes. I would simply take & wear 2-3 pair of pants for the 3 weeks without washing. You don't need to wash exterior clothing either (sweaters, jackets). So "laundry" for me is only socks, undies, a few tops.

If you start taking a bunch of stuff to do in room laundry (clotheslines, clothes pins, laundry detergent, sink stopper) kind of defeats the packing light purpose imo. Plus the waste of time doing it (if we're talking entire outfits).