Thanks for the suggestions, but I was hoping for a free one. I'm only going to use it to customise the apis, rather than using it for development. I've been reading a bit more about jedit, and I've gone off it a little. I found blue fish, and that looks a bit more useful. For example, you can mix html and php in it. Here is the bluefish home page.
http://bluefish.openoffice.nl/index.html