I've killed a bunch of headsets that way, too. Guess I don't have very good luck with wires.
I would go wireless, but the sound quality of FM transmitters isn't as good as the good old-fashioned cassette adapter. And I'm not going for some fancy in-dash custom solution (not until I get a real iPod, anyway).
Oh, and get a new one? Hey, that's twenty bucks. It's not the money, really, just the fact that a perfectly good piece of equipment stopped working because a bit of copper wire bent the wrong way one too many times.
The first thing I tried was cannibalizing the jack from an old headset and splicing the wires together with some heat-shrink tubing and electrical tape. It didn't work out so good (and even if it had, it was ugly as sin and wouldn't have lasted).
I did a little more research and then hit Rat Shack to pick up a real replacement jack. And a soldering iron -- I've never owned a soldering iron, and it's been a heck of a long time since I've used one.
The eHow tutorial on How to Replace a Headphone Plug was helpful, but when I followed the instructions, I had an extra wire (never a good thing), and when I tried it out, I was only getting sound from one channel.
I did a little more research. Oddly enough, the patent application for the cassette adapter was really helpful -- it has a circuit diagram. I eventually figured out that the extra wire was another ground wire and I could twist them together.
So, after a few lungfuls of solder, it seems to work. It's kind of ugly and sloppy, but I have a spare jack and a few extra feet of cord to make mistakes on, so I can always try it again.
Oh, and let's see the math:
New Cassette Adapter: $19.99
Soldering Iron, Solder, Headset Plugs: $15.72