I like keyboard shortcuts that put focus in commonly-used edit boxes:

Ctrl+E will put focus in the "search" box in Explorer for Windows Vista Beta 1.
Alt+D will put focus in the address bar in IE.
F11 will put focus in the "find a contact" box in Outlook, this is very useful for quickly looking up someone’s phone number.
/ (forward slash) will put focus in the "search" box in gmail (too bad this doesn't work on Google's search results pages).

That last one follows a well-established UNIX convention. In fact, I think more arcane UNIX keyboarding conventions should be brought forward to modern non-terminal-based applications. That’s why the edit box in IE’s history search allows you to type CTRL+U in order to clear the input field.  Some wag intern wired this one up.