One option that hasn't been mentioned is Warrior, Rogue, and Mage (a.k.a. WYRM). It's a small, free game intended to do the sort of things D&D does without being particularly D&D like. In a similar vein are games like Microlite20, which are generally closer to D&D but extremely minimalist.

I doubt you've had time to actually look into that many of the systems suggested thus far, but we're getting dangerously close to D&D edition warring here, and it's not even a D&D thread.