DropBox is the new FolderShare
I used to really love FolderShare as a way to keep a directory of files synchronized between a number of computers. It worked on Mac and on Windows. It was great for keep the "Documents" directory on macs synced with "My Documents" on PCs. At the time I used OpenOffice mostly, so it worked great.
FolderShare was bought by Microsoft at some point, and development completely stopped. Years went by, and the Mac version was never updated. It still worked, but was never enhanced or improved.
As I got more dependent on FolderShare, I had more and more files in it, and I would run into the file limit of the free version. I would have been happy to pay money to use a "pro" version, but there was no such thing.
Probably about a year ago, FolderShare started to get flaky on me. Maybe it was the newer versions of OS X not working well with the old, old client. Maybe there were changes on the service side that were happening. I don't know. It's hard to bitch about something that's free. One day, my entire foldershare directory was erased, boom. I'm not sure what happened, but I didn't trust it any more, and it seemed clear to me that a free file sync service for Mac/Windows users wasn't a huge priority for Microsoft.
So I started using the iDisk in mac.com/MobileMe. I've had a mac.com for years, but I only used it to keep my address book synchronized. iDisk has a sync feature, where there is a disk on all your Macs that is kept in sync over the network with your MobileMe storage. It's similar to FolderShare, except that there actually is a server storage component; FolderShare was just a reflector, and all storage was on your client computers. Unfortunately, iDisk syncing doesn't actually work. Most of the time, it says "the last sync failed" with no reason for it. Other times, it just won't sync at all. Occasionally, it will actually upload stuff, but you have to poke at it so much, you might as well manually maintain a disk on a server yourself.
I ended up turning off iDisk sync, and just using iDisk as a remote drive available only when I'm online. That kinda blows for obvious reasons. But at least it works, and stuff that I know I will need at home later, I can just drop onto my iDisk and get it. iDisk also only works on Mac, which is annoying.
But now I'm using DropBox. It's like FolderShare in that you can just create a folder on your computers. But it has a server component like iDisk. It keeps some level of version history of files you upload or delete. It also supports Windows, Mac and Linux. The client is really slick and unobtrusive; and the web UI is much easier to understand than FolderShare's was. And if you like it, you can actually buy 50GB of storage for $99/year, which is not a terrible price.
I hope they can operate profitably and stick around.