I just read this and thought I'd share. I got it from an e-newsletter I get weekly from Missussmartypants.com:

Here's what to do with your broken lipstick:

Put the lipstick into a microwave-safe dish. Mix into the lipstick the contents of 1 pot of Carmex lip balm (can be purchased at any drug store). Microwave for about 30-45 seconds on low. Stir to mix and then spoon back into the lip balm pot and let cool.

Now you have a pretty tinted lip balm in your favorite color! It sure beats throwing out an expensive broken lipstick!