Do you want just a simple transmitter or an FM stereo transmitter. Got plans for both.
I was looking to make an FM transmitter for my car. My wife has one that fits on her iPod, but I have an iPod nano, and it only has a headphone jack on it. I was looking for an instructable for a cheap FM trasmitter that I can plug my iPod nano into and play my tunes through my car stereo. any help is appreciated, thanks!
There's an open source project called the NiftyMitter and HERE'S an Instructable based on it with links to the main site.
In addition there is this instructable for a computer controlled version Hope this helps, Drew