Some of the comments on reusing the same clothes--especially under layers--over and over; I'm a little perturbed. When I was in the reserves I did only use one change of clothes with no shower/laundry for a week, but I rather think touring warrants a little more comfort.
It takes me no time to take my shorts, undershirt, and briefs, toss them in a plastic bag with camp soap and water and give them a solid wash! To dry use the air dryer provided over night and the next day. Should it be raining the next day, no problem. You sleep in your dry and clean clothes, your 2nd set. In the morning you put on the damp stuff, the still drying 1st set. Well, yes you will scream like a little girl the first 30 seconds, but it's not different than 5 minutes into your ride anyways! Why the third set of dry undergarments? In case your second one gets wet (i.e. it starts raining on the next day but you're already riding in your 2nd set, your first set is still drying). The third one is to always have at least one set of undergarments to sleep in when it's cold. You don't ride in your third set, it's there for emergency. Of course this doesn't apply if you have a different set of clothes around camp. I simply tour/commute/do all my riding in street clothes.