There is a sort of “rule of thumb” that I try to follow that makes sense.
If your work doesn’t exist on at least 3 different drives in at least 2 different physical locations, then it truly isn’t backed up. Some might even add at least 2 different types of media (magnetic disc + tape/etc…).
Personally, I keep my data on two different physical drives in my home, one primary that I normally work from, and one that gets rsync’ed to every night. There is a third drive at my office that also gets rsync’ed to every night. This was easiest as I could simply seed a large drive at home and physically walk it into my office. I also have a secondary Flickr account that I just sync all my jpg to for the heck of it (1TB of free storage with them, why not). Everything in it is private by default.
I’ve heard good things about crashplan or mozy (I think owned by Dell now) for creating another remote copy of your data as well as folks like Amazon. At the end of the day, as @Morgan_Hardwood already mentioned, chances are that it’s more secure with them than your own home network. 
Amazon glacier is for long-term storage that is not time-sensitive for retrieval (if you c.an wait several hours to get the data back). It’s also pretty cheap I think, like $0.007 per gigabyte per month.