what would happen if you put a regular cfl on a dimmer; say a leviton slide dimmer.

If it is non-dimmable it will not start at low settings, and will only start past a certain setting. Light output would be unstable, with a strong tendency to flicker, and possibly overheating the CFL ballast. Most lamps would fail in short order, either by the ballast fuse ( if present) going open, or by the bridge rectifier diodes going short circuit due to the high conduction angles imposed on them, and they are very optimistically rated to begin with in most cases.

Dimmable CFL lamps are designed to withstand this regime, and to start over a wider range of input voltage, and so stay lit continuously at low brightness, but still do not dim as far as an incandescent lamp before staying off or flickering.

In the worst case scenario, you will overload the dimmer triac, causing it to go short circuit, applying full uncontrollable power to the lamp. This would most likely coincide with diode failure in the lamp , killing both at the same time, and hopefully blowing a fuse rather than causing a fire in the lamp ballast.

wow!!

also what would happen is this story

thats really sad. 

A standard cfl or any switch mode power supply on a incandescent dimmer (triac based) is a very bad thing.  It is switching it on and off 120 times per second.  Each time it is switched on, there is a current inrush.  So look what happens to the electronics when it has to endure 120 inrush cycles every second.

I tried this very experiment on a cheap "Bright Effects" spiral CFL last week. It resisted dimming; it stayed at full brightness but started flickering, which became worse as it was dimmed lower. You could not dim it even 50% before it would go out. The ballast started to smell very bad very quickly so I stopped. The lamp worked fine in a standard socket after this but I figured I drastically shortened components in the ballast by doing this.

I may try this again to put the pictures back up after my surgery tomorow if I'm feeling up to it...The first time I did this it was weird, it stayed lit, but was smoking from the ballast and flickering like crazy, it was a cheap TCP CFL.