Sacha Mardou has several playing cards she's taken around to cartoonists and drawers of all sorts and had them doodle out some pretty cool stuff on 'em. I forgot that I did one of these and I came across her Live Journal page and found it. She has several other cards too, as well as (of course) her own very cool artwork.
Above (click for larger version) is: First Row: Jessica (Paperrad), Ben (Paperrad), Onsmith; Second Row: Zack Soto, Andy Roberts, Jason Robards; Third Row: Dan Zettwoch, Dylan Williams, Karen Schneider.
A sample of Sacha Mardou's work: