A couple of buddies of mine (Avi and Ken) both have Lomo cameras that they shoot with. For the uninitiated, these are super low tech cameras that are mass produced in Russia. There is no autofocus but instead a choice of 4 (count 'em -- four) focus settings. These cameras are so simple and bulletproof, that using them is more of a philosophy than a tool. The whole idea is to experiment and play. On top of that, the lens isn't sharp corner to corner and it has quite a bit if vignetting. That's okay -- it adds to the Lomo look. If I still shot film, I would pick one of these up right away. I may pick one up anyway. In essence, these cameras are the anti-digital camera.
If you aren't willing to go that far, there is the lensbaby. I have one of these on order. This is a super simple lens for you SLR. It is a single lens attached to some flexible tubing. You focus by using your fingertips to move the lens in and out. You can also tilt the focus plane. This lens also has quite a bit of blur and vignetting. And it works on digital SLRs? This thing is so old school that you have to manually take it apart to change the aperture. Sure, you could get the Canon EF 50mm f/1.8 lens cheaper -- and it has autofocus and an adjustable apature. But there is something cool about the look and feel of the images form this lens. Check out some of the photos here. (I want to post photos but I don't want to steal anybody's images.)