Might be of use to someone..

[toothycat]

ISBN barcodes use EAN13. This hacky evil thing will take an ISBN on the command line and produce an EAN13 barcode, along with the required human-readable bits (the original ISBN and the generated EAN13 code, which has to use a different formula for the checksum and needs '978' tacked on the front). It'll spew the result to STDOUT. perl codeEAN13.pl isbn | pnmtopng > out.png works nicely. Whitaker link to a load of places that appear to charge for the privilege, for some reason.

Update: Now in handy online form.