I am a huge fan of SugarSync. It is exactly the solution I was looking for to keep different folders in sync and backed up between multiple computers. For awhile they have had a free 2GB account but they sent out an email letting me know that they have raised that limit to 5GB. That is a pretty sweet deal. They are obviously hoping that you will use more storage and pay for it (I use 60GB) but if you are just using it for documents or a small music collection it is perfect.
SugarSync added streaming music capabilities to their BlackBerry client not to long ago so you can use these 5GB of free storage to keep all of your music in the cloud. I am still waiting for their client to let you sync your pictures from your BlackBerry to the cloud but that feature has yet to come. I do like how it gives me access to all of my pictures on my desktop from my BlackBerry.
If you don’t already have an account I highly recommend signing up for SugarSync on their website. You can read more about their announcement of free 5GB of storage at this link.