Well I prefer or used to the MTR series from REI but the quality has gone downhill, You definitely don't want cotton unless you carry a whole bunch of corn starch along with you.
I have started looking elsewhere and liking the feel of the Patagonia mesh and they both dry quickly and don't have any odor problems to date.
I know they are expensive, but the ExOfficio and Patagonia stuff is really, really good. You can take only 2-3 pair on a RTW and they would still be worth wearing/keeping at the end of it.
Another vote for the ExOfficio stuff. Two pair will get you anywhere. Cotton is not your friend. www.whitehorsegear.com usually has them at a good price...
Patagonia boxer briefs is one of the best purchases I've ever made. Yes they are pricey at $30, but well worth it. Great for travel and backpacking, I highly recommend.
I got some microfiber boxer briefs, made by jockey, at wal-mart. They were having a special, 2 pair for $7. Good comfort, wicking material, seem OK for the price. I also have some under armors that frankly are too slick - my pants fall down :Wow1:
exofficio unders are great. I have got seveal pairs. They hold up really well after serveral washing. They do not get those fur balls like several of the other.
I asked Scott this same question about a year ago. Best advice I've ever received. The ExOfficio underwear is nearly magical. Super easy to clean, very quick drying. I can sit on a leather seat for 12 hours in the Mojave desert and I never get sweaty or dank, never get ichy, and they are seemingly incapable of absorbing any odor.