The other posts that I found were through a search on "profitable weekend project" on Hacker News and it brought up quite a few projects.
Some of the projects were quite simple to implement, include www.whatportis.com. It just allows the user to enter a port number and it tells you what it is used for. The other interesting thing is that a simple site like this is a great server for on-line adverts.
So my motivation for learning Java scripting is to give me the tools to build these simple webapp. Perhaps getting more complicated as my skill set grows.