Together with Maperitive's scripting language and some Python scripts that I wrote, I have put together a framework that anyone can implement fairly easily to create their own tiles for a localized area and then host it on a web server (I am using Amazon S3 for my tile server). I hope to publish my steps in the next month or two.
And then not too long ago I discovered that the MapQuest Open Initiative made bicycle routing freely available based on the OpenStreetMap data. How cool is that! So now I can ride my bike while surveying for OSM and if I tag the paths correctly, everyone can route on them properly within a few days of me uploading the data.
You can see my BoulderBikeNetwork sandbox area at https://s3.amazonaws.com/boulderalf/boulderbikenetwork/google_map.html
Note: just today I saw this map http://www.cyclelicio.us/map/ that does alot of similar things that I have been thinking about. It is exciting to see the many uses for the OSM data!