Montreal-based app-maker DokDok is invading your email. And you'll love them for it.
Their website sums it up best:
Sharing documents via email happens daily, but managing attachments can be frustrating.
We believe that users should be able to easily verify that an attachment is the most recent version, track its changes, and share it with others—all without forcing a change in typical business workflow.
DokDok makes it easy and automatic for users to find, work on and share the latest version of any document right from their inbox.
DokDok enables users to experience email the way it should have always been. Smooth and simple. The dreaded attachment, the one that's updated fifteen times between six different people, is no longer a beast of burden. DokDok is the sword that slays it! Unfortunately, the app does not work with regular Gmail. You need a Google Apps account. Grab that here, and the app here.