I have been manually adding road names to previously traced data from the Statistics Canada 2009 road names dataset, which OpenStreetMap has got permission to use. I am currently adding road names to the wonderful 1970's-era "new town" of Bramalea, Ontario, Canada (part of Brampton now) where all the roads in a given area start with a given letter e.g. Addington, Albion, Alexandria, Aloma, Ascot, etc. See Wikipedia.

If you want to help, download the "road network" data from here. The license is compatible with OSM. Select the year (2009), the language (English), the format (several available, shapefile works best in OpenJump), and the area (Ontario). Then download a program called OpenJump, load the file, and start adding road names. Note that this data hasn't been imported directly into OpenStreetMap as the roads in that dataset don't quite line up with reality, but the road names are all correct and can be added with the assistance of Yahoo imagery, GPS traces or Geobase data.