There is tons of software available for Treo and some of it is free! Here are some of the free programs available:
Diddlebug: Diddlebug is a program that allows you to jot down notes on what looks like a yellow-sticky note. The program uses digital ink to record your information and is also capable of setting alarms for each note from a pop-up list.
SharkMSG: This program allows you to send an automated text message to callers when you are on the other line or are unable to take the call.
Directory Assistant: This program is very handy and is great for finding information on the fly. It's great for getting directions and information and you may find yourself using it instead of your PC!
TCPMP: This program turns your Treo into an entertainment device. Shrink down your DVDs using another free program, Fairuse Wizard, and then watch them on your Treo. This really comes in handy when you're stuck waiting somewhere.
Sound Recorder: This program allows you to make a note to yourself by storing digital files directly to your external card. It comes with a record volume and a playback volume, as well as recording quality level. You can even set an alarm to play your message at a certain time.
U*Blog: For all you bloggers out there, this free program will allow you to post your blog directly from your Treo! If you have something important to share with the world, open the application, type, and post. It's that simple. It's a little difficult to set up, but once you've got it, it's worth it.