F2: Rename the selected item
CTRL+SHIFT+ESC: Opens task manager
ALT-ENTER: Open the property dialog for the selected file
And for Internet Explorer:
F4: Display a list of addresses you've typed
CTRL+ENTER: Add "www." to the beginning and ".com" to the end of the text typed in the Address bar
CTRL+LEFT ARROW: When in the Address bar, move the cursor left to the next logical break in the address (period or slash) (update: my friend was kind enough to point out that this also works for most input boxes; ctrl-home works too; you can combine this with shift to select words too)
Oh... and check out this cool Free Software Sticker Book.