Since SpiderOak was submitted, I thought I'd suggest Wuala as well. Personally I've had better performance with Wuala plus there is a trick to extra storage for cheap. If you buy a LaCie flash drive (like a 32GB), you get the same amount of space on Wuala for a year. I did that and then sold the flash drive on eBay. A year of 32GB service cost me something like $8. That's a deal.
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