Hanes cotton boxer briefs for short rides such as local shopping errands. I'm going to try the Champions based on recommendations here.

For longer rides I switch between Baleaf faux-chamois padded undershorts (they're too short to wear without baggies or jeans) and AeroTech Pro shorts. Both are good values and comfy on longer hot sweaty rides, although the Baleaf padding is thicker than I'd like. I prefer lighter material for wicking -- I don't need the padding. The AeroTech seems to wick moisture away more effectively during swampbutt weather.