So I'm a bit of a theater geek, and as such I have a large collection of theater-related items laying around. A while ago, one of the theater directors I work with sent away to the major technical theater companies (Apollo, GAM, ETC) and asked for some stuff to show his students. Well, one of the things we received was a large number of gel sampler booklets. Essentially, these are small pieces of gel, about 2cm by 5cm, bound on an edge into a little booklet. These are about the same size as the average flash head! While they're certainly not optical-quality (they're scratched and fairly low-quality) they do work if you're tight on money or if you just want the occasional color on your flash for artistic effect! You can either rip out the colors you like most, or carry the whole booklet and tape it onto the flash (I do that, it looks extremely ghetto and very funny). You can get them from any theater or art supply store, and many photo stores have them as well, at least the ones around here do. Good luck, just thought I'd post what I found useful. See? Perfect.