The following sites may help:
http://www.jpos.org/
http://www.a2zss.com/products/ISO8583.jsp

The ISO standards can be found here:
http://www.iso.org/iso/en/CatalogueL...S2=240&ICS3=15

A detailed spec can also be downloaded from here:
http://www.trustedsecurity.com/Docs/...8583_v.1.4.PDF

Hope this all helps.