Donate to the Lead Adventure Forumto keep it alive!
Excellent thread, can it get stickied as this us a question that pops up on a regular basis?
D&D Battlesystem Skirmishes: THE game to get if you want to expand D&D rpg combats into fully fledged skirmish games. (Also the thematically similar, but more complex WotC version 'Chainmail')
World of Twilight is a great skirmish game with lots of characterful minis.http://www.worldoftwilight.com
Another wargame that I initially thought was specific to Arthurian settings but is actually more generic than that is the Dolorous Stroke. The author mostly makes RPG supplements and I have yet to actually try the game myself but from what little I have been able to gather it seems focused on extremely small scale skirmishes and uses a pack of cards to represent each character's health. I don't think there are any rules for minor enemies but there do seem to be some suggestions for them on the internet, which I can't find right now.