There are already some alternatives available for Google Drive, like Yahoo Briefcase, Xdrive, etc.

Which service do you use? (I'm in need of one, so maybe you can help me make my choice...)

Box.net is a really good service
http://box.net

I use MediaMax/Streamload (25 GB of storage) for free. You can download back to yourself up to 1 GB per month for free. For $4.95/U.S per month (save if paid by the year) you can download up to 10 GB/month.

Also, with the free service, send files up to 25 MB in size.
With the fee service unlimiterd size and hosting.
http://www.mediamax.com

Another service I just started testing out is Mozy.com.
http://mozy.com/, https://mozy.com/mozy/overview
They offer 2GB of free storage space. More for a fee. Requires client download. PC only. The site says a Mac version coming soon.

More services listed and reviewed:
http://www.pcworld.com/resource/printable/article/0,aid,125729,00.asp
Charts:
http://www.pcworld.com/zoom?id=125729&page=4&type=table&zoomIdx=1
http://www.pcworld.com/zoom?id=125729&page=9&type=table&zoomIdx=1

http://www.techcrunch.com/2006/01/31/the-online-storage-gang/

drivehq.com also not bad...:)

I have around 80 GB on this Schlund server which is enough for most things. Technically I'm not supposed to use it as a file storage system though, but only use it for web pages. But of course it's just a bonus of having this webserver.