What kind of back up software do you guys use?

I'm looking to get some back up software that'll back up my stuff to a external harddrive, or even an online backup solution for my home business. I'm in architecture and there has been situations were I've had file go bad and I've lost a week or so based on my own poor saving habits. i'd like something that would back up my work files nightly so the next time I get slapped in the face by reality I'm not completely screwed. I've done a little research myself and I'm just curious to see what you guys are using.