For Sprint, O2, you can use the one-time-purchase MyTether, which as of the newest version 2.10 is working quite well.
From the site
http://mytether.net/:
* Allows you to share your O2 UK, Verizon, and Sprint 3G from your Pre to your computer, iPod Touch or other WiFI devices.
* WiFi network name & WAP key customization options
* Makes your Pre into a MiFi-like Mobile HotSpot at your convenience to share your 3G connection.
* Converts Palm Pre into a Wireless Network adapter by letting you share the WiFi connection on the Pre instead of your 3G when tethering over Bluetooth or USB.
* Network usage graphs and total data usage for the session
* Reported to work with iTouch/iPhone, PS3, Xbox 360, Eye-Fi, and will probably work with your WiFI device!
* Ability to turn off the LCD without putting your device into sleep mode.
* Convenience features such as restoring the old WiFi connection when tethering is disabled, prompts to take care of pre-requesties to tethering, remembering settings and last tether options, restoring modifications to settings back to original value upon exit, and many more to list.