A good program for editing code with another person on another computer

What's a good program to edit code, or the same document at the same time with another person through开发者_开发问答 the internet. I need something where a friend and I can edit the same document at the same but he's on a Windows computer and I'm on a Mac. Something like Google Wave where we can just create a wave and edit the document at the same time, but I want something for coding. It doesn't matter if we can't compile on the program just to edit it, and later we can save and compile on our computers.

I've used SubEthaEdit. It works quite well IMHO

I think you are asking for an IDE that allows multiple instances to open common files and projects. I don't think that exists.

However one lower-grade alternative might be to simply screen-share. One guy programming, the other guy kibitzing. This could be done in accordance with extreme programming (XP) rules: http://www.extremeprogramming.org/