My house (and street) wasn't on OpenStreetmap (OSM), so I put it on there! I've got a phone running Android so I used the My Tracks app to record a GPS trace as I walked down the middle of the road along Yeoman Way.
Then I uploaded the trace to OSM, did some editing and now it's there, really simple. I've learnt that you have to do traces longer than about 100m, otherwise the whole process doesn't seem to work very well.
People wonder why I contribute to OSM. They shake their heads in disbelief that I'd do this work without getting paid. I think the key thing is that when you contribute to non-proprietary information, society as a whole benefits, and so I do too (being a part of society).
This is in contrast to, say, working in a shop for nothing. Working in a shop without pay would benefit the shop owner, but not necessarily society as a whole, and would not necessarily benefit me.