I'm slowing down from fall semester madness just long enough to mention that there are now not one, but two Zotero-related apps available for sale in the Android store:
Zandy, a client allowing library access/viewing/editing from your mobile device, and
Scanner for Zotero, an app that replicates some of the Zotero "magic wand" function by allowing you to scan ISBN barcodes to add items to your Zotero library.
I've tried Zandy just a bit and it seems to work fine for what I've done with it so far -- I haven't yet tried out Scanner, but both apps look promising and interesting. (Obviously, I'm not affiliated with either project.)
Edited to add: iPhone/Zotero users should take a look at BibUp, a project of the University of Fribourg.