
Quick and easy tip: I find myself using Preview.app quite a bit to read documentation (in addition to normal development tools), and usually zoom the currently active window to fill up the screen. Using the mouse in this case gets fairly tedious, so I took to mapping this command to a keyboard shortcut. While the mechanism for doing this is nothing new on OS X (it’s been around forever), few people seem to take advantage of it.
Mapping a keyboard shortcut to the Window->Zoom command (in Windows, this is uniformly accomplished via “Alt-Space + X”) helps a lot to quickly zoom in/out of whatever it is I am doing, but many OS X applications do not map this command by default. Enter the Keyboard & Mouse preference pane. This single change happens to work with many applications (Mail, iCal, Safari, XCode, etc). I find “CMD-/” to be a fairly reliable and easy to remember mapping.
This is a screenshot of a section in the “SystemPreferences->Keyboard&Mouse->KeyboardShortcuts” preference pane. As you can tell, I generally don’t customize my system that much, but this one is a no-brainer. Give it a spin and see how you like it.

So this tip is awesome. But it doesn’t work in all apps, even though Window->Zoom shows the universal keyboard shortcut.
Firefox, Postbox don’t work. Using Ctrl-Alt-Cmd-/ as the shortcut. Works in Safari, 1Password. Searched google for why it doesn’t work in FF, no luck.
Same here.
I’ve been using this trick for a couple years now and it never works in firefox. I was hopeful firefox 3 was going to fix it.
I see there is an extension that might help:
http://kb.mozillazine.org/Keyconfig_extension
I tried to bind a keyboard shortcut to maximize the size of the window in OS X and it does not work in Firefox. I think the reason is that Firefox has two menu items called Zoom.
View->Zoom is a sub-menu that controls the magnification of the web page, and Window->Zoom controls the size of the window.
OS X binds the keyboard shortcut to any menu item called Zoom, View->Zoom gets selected, and does nothing.