Amazon has huge amounts of excess capacity and sell it to corporations at very low prices.
Now they’re doing the same for online storage.
Jungle Disk has no minimum charges or monthly fees, is accessible from any OS, will backup your computer automatically, and costs a mere 15 cents per gig, much less than comparable services.
$20 for one-time purchase price, works on Windows, Mac, Linux, install on as many systems as you want. ($1 extra per month to access backups via browser, plus other features.)