I wrote a very simple bundle to run Python, PHP, Ruby, Bash scripts in Terminal.app without stealing focus from the TextMate window. I.e. you press Cmd + Shift + R, Terminal gets updated in background and you can keep writing code in TextMate.
More information and download: https://github.com/Cyberic/Run-in-Terminal-Bundle
It's very easy to add support for more languages.
Hope someone will find it useful.
Eugene / Dae