Megazoomer: Full-screen mode within any Cocoa app
Megazoomer is a free, SIMBL-based bundle that fakes full-screen mode within any Cocoa app, including Safari and Textmate.
There is one downside to Megazoomer: you've got to have SIMBL installed (head over to the official website to download it). Once installed jump to the Finder and navigate to ~/Library/Application Support, a reboot is not required. Create a folder called SIMBL, and another one called Plugins inside it. To finish the installation copy megazoomer.bundle into the newly created Plugins folder.
Running this tool is very, very simple: press Command-Return, and the front-most window grows to fill your entire screen, covering the Dock and menu bar. Press the same keys, and it shrinks again.