https://spideroak.com/ was recommended by Edward Snowden in one of his interviews as an alternative to DropBox. If you're not safe guarding anything super top secret than DropBox should meet your needs and is probably the best solution out there.
One of the key problems with SkyDrive/OneDrive is that there is no manual way to sync the data and sometimes it stops syncing. It's still a bit buggy compared to DropBox. Also, although Google Drive is a good free alternative I'm pretty sure you can count on them retaining your data forever and probably sharing it with the NSA or other US government branches...
With that said, if you're just uploading some family photos, a resume, etc. for safe keeping then Google Drive is just fine. I personally just wouldn't trust it with anything sensitive in nature.
If you have multiple computer systems, friends with extra storage on their machines, or don't mind shelling out a few bucks then there is also an application called Crash Plan, which is quite comprehensive in its backup capabilities.