What should I use for a good off-site backup?

A good backup strategy, such as Peter Krog's 3-2-1 backup is best. The idea is three copies of everything using two different kinds of media and one should be off-site. Klein mentioned Crashplan which is a good service. Leo also recommends Carbonite as a simple and reliable way to backup off-site. These solutions are designed to be easy and automatic. (Disclaimer: Carbonite is a sponsor).