DokDok – Turns Your Inbox Into a Document Management Tool
http://www.dokdok.com/

DokDok enhances your Google Apps inbox to make it easy to find, compare and work on versions of email attachments. Features include: a) Version history of email attachments; b) Summary of changes between versions; c) Related attachments in other conversations; and d) Other files exchanged with sender & recipients. This has been added to the tools section of Research Resources Subject Tracer™ Information Blog.