So I'm shifting/have shifted all my websites away from GoDaddy because their performance has been dire, however I am still left with an active hosting account of 10Gb webspace and unlimited bandwidth until June next year. I have no idea what to do with it really, but it would be pointless cancelling it and losing out on about £40.

The only ideas I can come up with are offsite backup or setting up an FTP, but thats it really. Any suggestions from the floor?

You could try offsite backup or setting up an FTP. 

I can see you've given this as much thought as I have

Coppermine Gallery? I have one on free hosting currently to keep all my photos highly available and backed up.

Pop Sabnzbd/torrentflux on it and have your own downloader

It is linux based, but I wouldn't know how to do that at all, I'm guessing i'd need SSH/telnet access?