I’ve been using a licensed copy of BC2 from Scooter Software for several years (I did not see the advantage to paying for version 3, but it is available).  I find it to be truly the most intuitive of all of the data synchronizing softwares out there. Everything that I have begun to imagine that I would need to do, they have a feature for, so I put my most important data on an external hard drive, back that up to a smaller one without some of the temporary, large media files I have, such as movies I will only watch once, then the more critical data I backup onto an even smaller hard drive which I leave at my mother’s house in another town.

This software even allows you to compare file by file on web sites/domains.  You can exclude whatever files or folders you don’t want to bother seeing again.

My only criticism (and this may be because I haven’t discovered where the feature is yet), is that there is no automatic way to remove empty folders when all of the files have been deleted from them.