M.L. Martin
Hero
Otherwise, I would suggest FATE. Of the few indie RPGs I could get my D&D group to try, it was FATE they had the most fun with. You can check out the main FATE site: FateRPG.Com: Fate: Fantastic Adventures in Tabletop Entertainment (TM)
There are currently three RPGs in print based on FATE:
Spirit of the Century
Starblazer Adventures
Diaspora
The upcoming Dresden Files RPG will also use FATE.
A fantasy version of FATE spun off of Starblazer Adventures--Legends of Anglarre--is also set for release late this year or early next.
Personally, I've got a soft spot for the HERO System (at least as an armchair system for reading and fiddling with), but it's decidedly on the crunchy side. For lighter stuff, I'd probably go with BESM or Dragonlance: Fifth Age, but they're both out of print. I should give FATE a closer look, though.