Sorry for the crosspost on the same topic and I'm sure the mods will remove it if it's inappropriate, but this seems an especially good spot for mentioning the Droid Pocket Guide by Jason O'Grady.
If you're new to the Droid, this is BY FAR the best introduction to the phone's features. The tone is conversational and non-technical. Lots of tips and it covers the subject in sufficient detail that you'll be well versed in the phone by the time you finish it.
No connection to the author. Just found it especially useful to give to my wife with her new Droid.
Amazon.com: The Droid Pocket Guide (9780321711939): Jason D. O'Grady: Books