Gurth offers a set of free wargames rules for using those Lego figures that your kids (or maybe you!!) have hidden under the bed.
When my kids go off to college, I’m going to have the biggest collection of Legos any middle-aged man has ever had.
lego
Bricks Only Wargame
Bricks Only Wargame is a set of free wargames rules for wargames using Lego bricks.
Two Page Lego Minifigs Rules Set
Consortium Games offers Minifigz, a two page rules set for battles with Lego minifigs, and similar mini people. I’m going to have to give this a try.
Update: The original link is dead. You can still find Minifigz on the Wayback Machine.
Mobile Frame Zero Lego Rules
Mobile Frame Zero is a set of free wargames rules (although you can pay, too, if you like it and can get a printed version) for playing games using Lego and other construction toys. It is very well done.