A maximize keyboard shortcut for OS X
One of the things I miss in OS X is the ability to use a keyboard shortcuts as often I do on Windows. Although I am learning new keyboard shortcuts every day, OS X still feels like more of a mouse-driven OS than Windows. Case in point: Under Windows you can press Alt + a letter to reach any menu in an application directly. The closest I've found to this in OS X is to enable the Move focus to the menu bar option (Ctrl+F2) which places the focus on the Apple menu. Needless to say, it's more tiring as you have to move manually to the menu you want, which may be on the other side of the screen.
Another feature I miss from Windows is the ability to maximize the current window using a keyboard shortcut. On OS X, you can maximize an application (or, depending on the application, change its size) by using the green plus key on the top-left of the window. Unfortunately, OS X doesn't give you any way to add a keyboard shortcut to this key short of writing an AppleScript. Thankfully, this is exactly what Simon Dorfman has done. Check out his script and instructions for adding a keyboard shortcut to the maximize button under OS X.
[Update] I forgot to mention that the above hack uses QuickSilver to add the keyboard binding. QuickSilver is one of those applications that leave you wondering how you ever managed without them.