I'll join in
1.
http://www.conceptart.org - learnt more looking htrough this site in a couple of hours than I had anywhere else.
2. The old Heavy Metal mags I've got littered throughout the office.
3. Anything by Mignola, McKeever, McKean, Bisley, Kelly Jones, Sienkewicz, Miller, Keith that I've got lying around.
4. Night, Dawn and Day of the Dead (Romero versions).
5. My ever-increasing army of MOTU figures (don't ask:))
6. Forums like this,
http://www.digitalwebbing.com and many others...
That's about all I can think of for now.
Simon