I've been having fun playing with the OS StreetView raster data. I've been tweaking roads around my house and lining up woodland with it. It's also great for building outlines (if not terribly detailed) but so far I've restricted myself to doing buildings in industrial estates.

The University of Warwick is now looking a lot better too.

It's not perfect data but it's useful for when I'm not getting a chance to get out and about with my GPS device.