For a while I've been wondering about a solution to the "I want to transfer a file from our laptop to my office computer" problem. OK, on the grand scheme of things it's not that big of a problem - I can always use a memory stick or save the file as an attachment to a draft in gmail.
But it always seemed to me that there should be a much simpler solution for two computers that are both online (but not on the same network). A couple of days ago I installed Dropbox, which has an open-source Linux (as well as Windows and OS X) client and is very simple to use.
It just puts a Dropbox folder somewhere of your choosing on your computer, and anything you put in that folder automatically gets uploaded to it's website (where you can access it from anywhere with your login) and downloaded to any other computers you have Dropbox installed on.