I've mentioned this time and again. I'm a fan of using keyboard if it's faster than reaching for the mouse. OS X has some great shortcuts and here's 2 more.
To be able to select from the available menu items in the application you are using:
CTRL-F2
To be able to select shortcuts in your dock:
CTRL-F3
Enjoy!
2012/01/21 Update: Apparently, these keyboard shortcuts no longer work in Lion (OS X 10.7+). No solutions for a custom mapping, as I'm a fan of native keyboard shortcuts because I'm often on someone else's computer. However, there are ways to customize the keyboard shortcuts by going to System Preferences > Keyboard > Keyboard Shortcuts.
