I have been working on the South Melbourne/Port Melbourne area where I work, which was not mapped at all. I am from Hobart, Tasmania originally, and have filled in some details from memory for the Hobart map.
I have an iPhone 3G with MotionX-GPS and OSMTrack, which I can use if I'm in a more remote area, but most of my mapping has been a combination of surveying and tracing the Yahoo! aerial imagery. I've also been filling in some street names for already traced streets from the public domain Collins 1936 maps in the Northcote, Preston and Hawthorn areas.
Also marking in universities, schools and parks as I see them.