Not so much a hidden one, unless you were not aware that for personal use and under 2GB, Mozy is free.
What is the best online backup software you have used? What is the worst? I know there are alot of complaints about every single one so which are the hidden gems on the internet? Backazon.com has live technical support, an actual person, and is a small company using the Amazon S3 servers. That is my little gem i've found, what are yours?