I'll plug SpiderOak here. Pretty decent prices and service, but their client was pretty awful the last time I used it... and encryption vastly slows the file sync (at least, it seemed so).
Thank you for chiming in. I am a paid user of SpiderOak. And it is great... when it works. I was able to get through rather complicated interface and I am OK most of the time with slower sync performance, but sometimes it just breaks out of the blue. Also, the client is not open-source. Granted they have open-source projects on the same infrastructure (nimbus.io) but this is something else.