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I've always liked Delicious Library for the Mac (you can scan in any book, movie, music, or video game, the application grabs the data, and puts it on your "shelf) - but, Barcodepedia (cross platform) is all web based, so - you could potentially have online communities of folks sharing/trading etc. Might also be an easy way to get stuff up on ebay, just scan and post...
"Barcodepedia.com is a community based online barcode database. The database is completely free to use, and everyone is welcome to contribute. Although it is possible to create a user on Barcodepedia, you can use the entire homepage without one. Originally the page was named barcoder which was a tech demo of of the new possibilities in flash 8, but due to a large interest in the subject the current more community minded homepage was developed." - Link.
