I found this blog called warkitty.com. It's mostly wicked funny, but there's a bunch of stuff that's in pretty poor taste and there's some profanity, so I can't say I would highly recommend it. There's a section on the sidebar with links to motivational posters. Again, above rule also applies here. But these are relatively clean. Okay the first one, not so much, but I couldn't help myself; also I blacked out a dirty word in one of them. Anyway, they cracked me up:
"I got a fee-vah!"
3 hours ago