For my gels, I used the plastic tops of yogurt pots - these are available in a large variety of flavours (I mean colours), are cheap and readily available, and they are considerably more durable than regular gels. They also clip very nicely to the front of my SB-26's (if I have a loose one, or if I need to have a strobe facing downwards, a small bit of Blu-Tac will hold it in place).
The only downside to these is that they don't transmit light as well as gels, so you need more power, but for my purposes, this was never a problem (as you see, I didn't even bother scraping the writing off the lids)Here are the results - one backdrop, various lighting. And this is before I even start playing with cookies, more than one colour, shooting the strobe through glasses (with or without water), etc, etc, etc. Who needs loads of backdrops?
(If you think that's good, have a look at this!)
P.S. Happy Thanksgiving!