Have you seen this article in Fortune? It looks like PDAs are more mainstream than I thought.
The Palm Education Pioneer grants have posted their findings on current pilot projects. While there seems to be lots of talk of how to integrate handhelds into the curriculum, none of the schools I have talked to or the participants in the PEP grants (as far as I can tell) have included their libraries/media centers in their projects.
Another good site for school librarians investigating handhelds is pdaED.com.