Look around for broken LCD monitors and TVs. (In particular, look for ones where the LCD panel itself is damaged, but the backlight works.) Then remove the main board and LCD (jump some pins on the power supply board to turn it on and connect a 555 circuit to provide the PWM) and you have a dimmable fluorescent lamp!
Or if you want to build your own, Linear has some good app notes on how to do it.
Of course, everyone's going towards LEDs nowadays. If you can wait until after Christmas, you might be able to pick up a lot of white LED lights for cheap. (Strip them down and rebuild them with a better driver.) Don't expect very good LEDs, but they should still last a long time if you derate them.