Several interesting services have appeared recently that use a Google Maps interface to allow you to draw bicycle routes and then get various stats, store them, search for routes, etc.
RouteSlip--some nice features & will make an elevation map for your route. Allows a certain amount of route editing which some others don't. See MO routes here.
Wayfaring--not bicycle-specific but allows tagging and has other features good for bicycling
GMap-PedometerUseful and easy for plotting a route but doesn't allow them to be aggregated or searched as most other services do.
RouteSaver - created by St. Louis cyclist Dave Ploch, this is be the best of the bunch in many ways. You can save routes, make route sheets, import and export GPS data, generate elevation profiles, view topographical maps and several other useful types of maps, edit the routes in a rudimentary way, and do many other useful things.