Windows only: Free application DropboxPortable makes the popular file-syncing application thumb-drive friendly, so you can access your synced bucket from your thumb drive no matter what computer you’re using.
Downloads: DropboxPortable Syncs Files to Your Thumb Drive
I finally gave this program a test run and I was pleased with the results. Recently I split up my KeePass password database into three databases, work, charity work, and personal. I kept a copy of the files on a USB dongle so I could deal with the occasional emergency at work or at home. I used SyncToy to keep the files synchronized but I have screwed up on more than one occasion and updated the passwords in two locations without synchronizing first. DropBox has the potential to eliminate that problem. I am slightly uncomfortable with storing a strongly encrypted password file in the cloud but I am pretty sure there are much easier ways of getting my passwords than cracking this encryption scheme.