Treonauts pointed out two inexpensive utilities that help streamline keyboard use on the Treo 650. KeyCaps600 helps Treo 600 and 650 users to type faster by providing alternate ways to enter capital letters, punctuation, and symbols.
KBLightsOff provides a mechanism to toggle the keyboard backlight on and off. This is an important battery-saving technique when using a Treo 650 to watch video, read eBooks, or listen to MP3s.
Both of these programs are small and cheap. You can pick up licensed versions of each for $15.50, and help the developers of these utilities continue to support and enhance them.