Handhelds.org has a great deal of detail on how to use Linux on handheld devices, such as the DEC/Compaq/HP "iPAQ" palmtop.
I've long had an interest in barcode use for Library applications; see Thokbook and Thokbook design notes; also the Symbol SPT1700 Palm-based scanner driver.
The long term goal is to produce a usefully integrated package for using an iPAQ as a "library wand" - quickly scanning in new books, old books returned to shelves, books being checked out (along with scanning barcodes on patron library cards), as well as scanning books at stores for comparison with pre-stored or online wishlists.
In the short term, we have at least gotten as far as producing apps which can talk to a scanner device (the In-Hand Scan from Socket Communications, using the Symbol 923 compact laser scan head.) We still need more of an architecture and applications, and support for more drivers (most of which are serial rather than CF.)