While doing the previous post, I stumbled on the "make-your-own" demotivator site at www.despair.com. Just upload your picture, type in a description and you can download it to your computer (you can also buy an 11x14 print for $13). I fooled them and made a "positive" poster!
PS...you can buy some really cool stuff at this site for the pessimist in your life. One of my favoriates is the "Half-Full" coffee mug! Oh, and I tried to buy this shirt for myself, but it was out of stock!