I usually don't backup anything on my personal computer. I know. I know. But honestly I just don't have anything that important on there - everything is in SVN or stores somewhere safe. My wife on the other hand is a different story. She's doing a lot of illustration work these days for her company Your Door and More and her hard drive was filling up with Illustrator and Photoshop files.
Originally I tried Mozy's free account. They give you 2GB of space and overall I was very impressed with how things worked. But a few months after signing up we got a message indicated we were over our 2GB quota. I knew we could upgrade and pay a small monthly fee but I wanted to explore other options as well.
After digging around and looking at several other services I decided to cancel our Mozy account and move to Jungle Disk. Jungle Disk is simply a client you install on your local PC (they have clients for all THREE platforms - Win, Mac AND Linux!). Your files are then actually stored on Amazon.com's S3 Storage Service.
Setup could not have been easier. I signed up for Jungle Disk, purchased ($20) and downloaded the client and during installation it guided me through signing up at Amazon. Everything was tied to my existing Amazon account as well so I didn't have to enter any new information - nice!
The Jungle Disk client (on Windows) is very well thought out. You can either setup a 'backup' plan allowing you to configure scheduled backups and selected data and/or you can choose to setup a 'network drive' which allows you to treat the Amazon Storage Service like a local drive allowing you to drag and drop files to it as well as share that drive among several computers.
Fees are dirt cheap. My wife probably won't be moving much data other than uploading backups. Mozy was $4/mo. With Jungle Disk charging $.15/GB our costs should be under $1 month for some time.
Other pluses - you can choose to encrypt your data. You purchase one Jungle Disk account and can then use it on as many computers as you like. It's possible to subscribe to backup reports via email or RSS.
Downsides? Not many so far. You are trusting your data to the 'cloud' so downtime could be an issue but for us that is not a huge deal. Web access isn't included but can be purchased for $1 month. This allows you to access your data via the web instead of having to download the Jungle Disk client. Again not a big issue for us and they do have a 'portable' version of the client which you can store and run from a USB drive.
I haven't installed the client yet on my Ubuntu workstation but I will report back once I have done that and used it for a few days.