I do a lot of work with graphics and have hundreds of .ai files, pdfs, etc. laying around. I would pretty much be screwed if I lost any of that material.
Since my motherboard doesn’t have RAID I was set out to find a piece of software that could sync my files to an external hard drive. I came across this after about 5 minutes of searching; Allway Sync. It is not a very pretty piece of software and I think the UI could use a lot of work, but it gets the job done well. You can have it simply do a backup or what I am using is the All-Way Synchronization which takes the newest changes. For example, I could take my external to work, change some files, bring it back and it will automatically sync my desktop folder with the newest files. Also, I have Automatic synchronization enabled so that when my external is plugged in via USB any changes I do within the directories I have chosen for synchronization, the syncing takes place immediately. Doesn’t slow my system down at all and only uses about 47Mb memory usage to run in task manager.
I highly recommend Allway Sync, also, it is completely free [http://allwaysync.com/index.html]