Running a small shared web/services hosting is an option. Put in a web server and let people host their sites on your server, for a fee. Or put a virtual machine and rent that whole thing. There is always people wanting a server of some sort and wanting to pay for one, that could be an option if you have enough CPU/HD. Having a website of yours and monetizing it is of course an option too. A combination of all those, plus some other ideas is also good when you have some capacity to spare.