The Vario rack was mentioned upthread, and it is cool. Provided the light 11lb/5kg max load is acceptable, it's fairly versatile and looks like it provides some neat, stable carrying options.

Like the similar Xootr, both of these have a quick release system that allows the rack to move between bikes easily, but neither have a quick release seatpost bracket, so it means that even when not using the rack, there's a remnant mount left on the bike, which I don't really like. If someone could design a mount that came quickly and fully off the bike (and could still handle 20lbs; I'm usually carrying bottles of wine! ) I'd be a really happy camper!