GmailFS provides a mountable Linux filesystem which uses your Gmail account as its storage medium. GmailFS is a Python application and uses the FUSE userland filesystem infrastructure to help provide the filesystem, and libgmail to communicate with Gmail.
This looks like this could be really neat. The only issue is that Google is supposedly starting to play authentication games now to block third party apps from connecting. Wouldn't it be in everybody's best interest for Google to write a full API for Gmail?