[ALUG] Document Imaging systems

Does anyone know of an OSS Document Imaging System for Linux ? Specifically I am looking for a system that can batch scan invoices and delivery notes and then file them using a printed invoice/delivery number in either an integrated DMS or perhaps populate a MySQL database. Even filing them a filename generated from the invoice/delivery number would be sufficient. Essentially I want to make approx 7000 printed invoices a month available on an extranet (Possibly integrated with a CMS like Mambo) I have found a couple of non-free systems (1mage and others) but these are all either too expensive or too feature rich and I would far rather do this with OSS if possible.