For those who are not familiar with Dropbox then you are missing out on what is the simplest and feature rich file sharing application I have used.
I came across this when I was having trouble with the Windows XP offline files feature. Essentially I had a few users using a mapped drive to a server and then sharing files within. The troublesome bit comes when you want to take these files offline and work on them away from the office. The offline files feature of Windows XP was becoming a constant pain where certain users synchronisation had stopped working or folder structures did not update correctly.