Google Mapps 4.2 gives bike route directions and maps.

Bike enthusiasts got a treat this week from Google with the release of an app for biking route directions. Called Google Maps 4.2, the app, is available at the Google Android apps marketplace and is compatible only with phones running the Google Android operating system vesion 1.6 and higher.
The apps can work either in the direction mode with the touch of the bicycle icon on the screen, or as one of the layers of the Maps app.
In directions mode, the app will give you a route favoring roads that are considered good for cycling, roads with bike lanes and bike paths.
When open as a layer of the Google Maps, the app will highlight bike-only trails showing them in dark green, while showing roads with bike lanes in light green, and roads Google considers good for cycling get a green dotted line.
Google is said to get the information it displays in the app from different sources like bike organizations, bike maps, municipalities and riders who send in routes.
At this point, the data stored is said to cover nearly 200 cities all in the U.S.

For more, see CNET.com