I'm very old, IBM 360 anyone!
It's much better if the subject matter is interesting. I've worked on all sorts of problems from accounting (ugh) to robotics (Yea) in many countries in the world.
Currently I'm working on a way to use computers to help seniors and their carers live better lives. The carers are busy and there are more seniors than ever before. It's called Stay-in-Touch.ca and runs on an Android tablet or a dongle.
I have a specific need (apart from meeting a super salesman) to port some functionality to send pictures to grandma from an iPhone, from facebook, twitter and so on. We can do it from Android, of course. Work on your own and sell the apps. I provide the API. There is an infinity of projects in this vein.
(Apparently this old programmer can't figure out new lines in slashdot!)