I haven't done this, but I've heard of folks doing it.
Here's one thread where someone claims to have got all three to work:
Then there's this guide to Windows on a Mac with some passing references to Linux and Ubuntu
And this blog claims to have found the way
You can search triple boot os x windows ubuntu and come up with a lot mor epages relevant to your research.
Good luck! Let us know if you get it working.
i've seen it done..but i personally dont know how to do it, can someone point me in the right direction? right now im dual booting b/w os x, and windows.