While giving presentations, I often find it necessary to zoom into the directory structure in the TextMate Drawer window or other parts of the window. I also find a need for this when I want to show some part of the window to someone a couple of feet away. It is very easy to do. Here are two ways:
1. Hold the Ctrl button and run two fingers (index and middle) on the track pad up or down. Alternately, you can hold the Ctrl button and use the middle button of your mouse to move up or down. Then let go and simply move the mouse to areas of windows you like to view while the window is zoomed in. You can modify the settlings for this (like ability to navigate the window while zoomed in) by changing the options next to "Zoom using scroll ball while holding" under the Mouse tab in the Keyboard & Mouse settings.
2. If you're like me and don't want to touch that mouse (or track pad), you can achieve the above operation by holding Applet key, alt key, and pressing the = button. You can then zoom out by pressing Apple + alt + - keys. Again, to configure this, go to Universal Access and check out the "Zoom" options under the "Seeing" tab.