GMail Filesystem over FUSE
There is a Debian package which allows you to use GMail storage as a filesystem written by a nice guy named Richard Jones. He has a nice web site dedicated to it.

But, this implementation uses is based on something called libgmail which accesses GMail via its web interface. Unfortunately, that web interface changes constantly and libgmail not been able to keep up with the flux and is not working any more.

So, I went and stole Richard's code and improved it. Instead of using libgmail, I just used python's imaplib. GMail's IMAP interface should be pretty darn stable and not likely to break.