Draw Something 2 is a social drawing app by Zynga, it's used by non-artists as well as amateur and professional artists. DS2's basic purpose is as a pictionary style game but most serious artists I know have long stretched and redefined its purpose for their own artistic pursuits. There are ink limits and tool limits and still the art that comes out of this app is incredible!
As a member of the popular Draw Something artist fan-site Draw Something Fanatics, I've seen an incredible amount of geek art and fan art by some amazing artists (and drawn some myself). So, without further ado, have some Whovian art!