Thanks for all of the suggestions. I downloaded and tried most of the products suggested above and, in the end, decided there must be something to this paying thing. I couldn't find anything that is as easy to use as GoodSync so I bought several licenses for that product. I don't want to store my stuff online; I just don't trust the sensitive data to the cloud just yet. GoodSync makes syncing up to multiple flash drives from multiple PC's a breeze. The only thing I wish it could do is to 'analyze' multiple jobs at once instead of forcing me to analyze each one individually before performing the sync. It takes all of about five minutes, but that still seems annoying.

I might experiment with some of the others for other purposes but this one does it all for me, and I landed on it after trying many others (most of which weren't suggested) first.