One of the difficulties one has biking in a big city is figuring out a good route — biking lanes, not too much traffic, scenic, and time-savvy. Ride the City is a website and iPhone app that lets you pick a good bike route (safe, safer, or direct) between any two locations in New York City, Austin, Chicago, Louisville, San Diego, Seattle, San Francisco, Toronto, or D.C. The app gives preference to low-traffic streets and those with designated bike lanes and paths, and it factors feedback from actual cyclists into its route choices. The map data comes from OpenStreetMap (a volunteer mapping project), and the app is available for $1.99. Check out the web version here
Related: Survey: Do You Bike to Work?