LowEndMac.com has published a couple of articles on Palm today. One was originally published in 2007 and the other is new. A piece on Handspring is forthcoming.
A History of Palm, Part 1: Before the PalmPilot | Low End Mac
A History of Palm, Part 2: Palm PDAs and Phones, 1996 to 2003 | Low End Mac
Dan Knight has also created a Palm OS User Group on Facebook: https://www.facebook.com/groups/1574006749575467/