Google now is offering bicycling maps. You can access this easy by going to Google Maps and clicking on "get directions" then dropping down the menu and choosing "Biking"

According to Google's Blog:

Today we've added biking directions and extensive bike trail data to Google Maps for the U.S. My team has been keeping close tabs on all the public support for biking directions that’s been steadily coming in, but we knew that when we added the feature, we wanted to do it right: we wanted to include as much bike trail data as possible, provide efficient routes, allow riders to customize their trip, make use of bike lanes, calculate rider-friendly routes that avoid big hills and customize the look of the map for cycling to encourage folks to hop on their bikes. So that's exactly what we've done.

We've also added information about bike trails, lanes and recommended roads directly onto the map. This can help you get a better sense of your route, or let you find trails nearby for a recreational ride. When you're zoomed into a city, click on the "More" button at the top of the map to turn on the "Bicycling” layer. You'll see three types of lines appear on the map:

• Dark green indicates a dedicated bike-only trail;
• Light green indicates a dedicated bike lane along a road;
• Dashed green indicates roads that are designated as preferred for bicycling, but without dedicated lanes