Don't know if this is common knowledge yet, but I'm posting it anyways...

Factory Palm Batteries for the Pre/Pixi/Centro etc. for $2.75 with free U.S. shipping. Sold by TheBatteryOnline via Amazon.com.

You can also get a package with the battery, Palm AC charger, and Touchstone for $19.65 via the above link (towards the bottom of the page) but the Touchstone doesn't ship for free (admittedly, not as good of a deal as buying the charger/touchstone via Verizonwireless.com).