There's a new tool here for mapping bike shops in Openstreetmap:
Bike Shop LocatorBasically, you can go to the map view of that tool, and then look at the bike shops it shows in your area. Then check whether or not they are mapped in OSM.
If they are in OSM, then mark them as such.
If not, go out and survey them, then add to OSM in the usual way.
Its based on a database from the Association of Cycle Traders, so includes most bike shops in the UK. Though the locations are not very accurate, so still a good idea to survey on the ground. Plus it might include a few mobile repair or hire services etc - without any actual shop at that location - so worth checking.
Some more details here:
CycleStreets » Blog
