You could use gmailfs if you have linux, it's awesome:
http://richard.jones.name/google-hac...ilesystem.html
There is also this app for windows that does the same thing, I haven't tried it yet myself:
http://www.viksoe.dk/code/gmail.htm
It mounts the mailbox as a drive, allowing you to store files there. Keep the 10 MB transfer limit in mind.