for me. Thanks and +1 for your generosity, cw8!
Also, a little promotion in the Giveaways' Directory: http://www.gog.com/forum/general/how_does_one_make_a_gift_aka_gifting_on_gog_for_dummies/post650
I usually write a text file with the usernames of the contestants (copy-paste). Then I use the List Randomizer (in the "Lists and Strings and Maps, Oh My!" section of random.org) to make the draw.
Choosing a post number have an issue: a poster with multiple entries (replies, comments, bumps) will get better odds if you don't check properly. Not a problem with usual contests, maybe, but go figure in Xyem's or Ian's weekly giveaways... ;)