How can I switch between textmate and terminal quickly?
There are a couple of ways doing this.

The quickest and easiest is to use Spaces.

Put Textmate on Desktop 4 and Terminal on Desktop 3

Then you can use ctrl-option and either 3 or 4 to switch between the two.

Personally I use Keyboard Maestro for this. I used to use a Service and a keyboard shortcut but a "feature" of the new security system makes it impossible for a Service to use the System Event library unless you turn on accessibility for every app. You need that to select "Bring All to Front".