I may be a Johnny-Come-Lately, but I've been perusing the rules "In The Emperor's Name" and I'm really impressed! It's a skirmish gamed set in the Warhammer 40k universe but it could be adapted for other wargames as well.
I've been on the outs with GW for a few years but this may rekindle some interest in the 40k universe. After all I've got quite a few figs sitting around collecting dust. Who knows, maybe I'll give 40k in 15mm a shot as well!
If you're interested you can download the rules for free here!