Here we are at unlucky for some Thing 13.
File sharing. In our library and indeed at the hospital where the library is based there is a thing called the Workgroup on the 'W' drive on each of the computers. This allows each department to share their documents and files. Every department only has access to their own Workgroup. So.. the ideas here like Google Docs and Dropbox are in themselves very clever and useful, but we wouldn't be using their services at my workplace.
Of course I can see their usefulness outside of the work place. If you wish to share your files and documents with another party this would be an excellent way to do it. Regarding Dropbox - very handy if you don't want to send loads of photos via email and clog up someone's inbox. Also very handy that the other person doesn't have to have an account with Dropbox in order to view your files.
At home however a wireless connection that allows pcs to 'talk' to each other would be the answer here. We did buy one at home ages ago, which allowed a wireless internet facility too, but we couldn't get it to work. Perhaps we'll have another go at some point...