• ctrl-u - Toggle the update area
• ctrl-r - Add @screenname of the selected Tweets user to the update textbox
• ctrl-q - Quit. Exit. Vamoose.
• ctrl-o - Open the options dialog.
• ctrl-1 - Show the "Recent" tab.
• ctrl-2 - Show the "Replies" tab.
• ctrl-3 - Show the "User" tab.
• ctrl-4 - Show the "Messages" tab.
• F5 - refresh. It seemed best to stick with IE/Firefox's refresh key.

Code added by lazycoder, modified by Alan.