I am a happy customer of ExpanDrive (http://www.expandrive.com/) which is very similar, except that it is cross platform and looks like it support more back-ends.
ExpandDrive recently greatly enhanced their product by providing background uploads.
Cyberduck (and apparently Mtn. Duck, judging by the screenshots) is equally cross-platform; which is to say, runs on recent-ish versions of OSX and Windows. Expandrive looks decent, but for my purposes fuse is good enough, and free.
ExpandDrive recently greatly enhanced their product by providing background uploads.