There are 2 barcode sleeves made by Symbol. One is scan only, the other does scanning and 802.11b. They can be found at
http://www.dreampages.com?aff=pocket...ge=bexpac.html
Nexian is coming out with a camera sleeve which is also on teh above page.
There are also several compact flash and pcmcia type scanners by Socket for the Pocket PC. They can be found at
http://www.dreampages.com?aff=pocket...ortableb1.html