For online backups I use CrashPlan. They recently changed their pricing, but when I signed up I got a the "Family Plan" which cover 3 computers, unlimited storage, etc, etc. for $60/year (with a 3 yr plan.)
Even with an online solution you have to plan ahead because it takes a good two months (or longer when running part-time.. unless you're Williams and have your computer running 24/7/365) to back up 700+ GB, so it's best to make a local backup just in case.. CrashPlan also provides (for FREE) the ability designate another computer to backup your files to. This can be a family/friend computer in another house, state, country... Your data is encrypted, so you don't have to worry about wandering eyes. More here: http://b5.crashplan.com/consumer/compare.html
Regardless of your preferred backup method it's always a good idea to backup your data OFF-site in case of fire, earthquake, etc..
If you have an anti virus program like AVIRA then it comes with a built-in backup/scheduler. This is my preferred method for local backups.
Or... Windows comes with it's own utilities. I have no personal experience with either of the following, but found them after doing a quick google search.