First of all, I really like 40K from it's beginning of Rogue Trader to it's current edition. It has a great background and lots of resource material. Recently I have been checking into Infinity, a skirmished level game.
I have found some spreadsheets that convert 40K material to Infinity, but have also been looking into other fan made material base on the 40K. All of it is pretty interesting.
Fan Made Skirmish Rules
In the Emperor's Name
KIllzone
Kill Team
