Side-projects channel on SSG Slack is very interesting. These are things we personally gravitate towards during off hours and can't stop thinking about... usually not for immediate financial gain.
SSG is my side project. I have absolutely no idea if/when it will make any money but I don't care. It's a community that I believe needs to exist.
@tectonic's side projects are Huginn (https://github.com/cantino/huginn) and SelectorGadget (http://www.selectorgadget.com).
Join us on http://bit.ly/joinssg. About page is http://bit.ly/coolssg.