A really neat feature of TextMate is the ability to call it from the command line and pass a directory or file as the object to open. Works great.
For this to work, you need to run a quick one-liner on the command line:
sudo ln -s /Applications/TextMate.app/Contents/Resources/mate /usr/local/bin/mate
Once done, you can call mate and pass it any object you want to open, such as:
$ mate my_rails_app
and it opens the entire directory as if it were a TextMate project.
Lots more detail available here: http://manual.macromates.com/en/using_textmate_from_terminal.html