One of the products that I use on a regular basis is Allway Sync.
It allows me to manage files between my desktop, notebook, and portable drives so that my files are always up to date when I use them, where-ever I need them.
It is very reasonably priced and having used it for more than 2 years now I have no hesitation in recommending it.
While there is a Free for Personal use version, with some limitations, I think the US$25 / AU$30 price of the Pro version is not too much to pay for a quality product.
Once installed it is a simple matter to pick a source and target folder and start Sync’ing.
And after the first sync process every sync is quicker and shorter as most of the files are already there.
As a backup process it simplifies making copies of files and speeds up the process by only grabbing the files that have changed. Using multiple folders on multiple USB drive means that you could be making redundant backups easily.
Click on any of the images above to order Allway Sync in Australian $ at approx. $30 for a single user depending on the current exchange rate. Order Allway Sync through Digital River.