Experimental pure Javascript web application. This has been done just as a toy application, to test the capabilities of Javascript. This does not have any real practical application, but this does not stop me from pitching it, so here it goes:
Do you have books you could lend?, you know, a book dies by collecting dust in your library. Do you know people who have books you would like to read?, same, for them.
You could lend book from your people, and vice versa, but where's the fun with that? With this application, you and your buddies can build a distributed library, so, if you want a book, you can search and borrow it.