Extra cool feature: Seattle/Puget Sound area map overlays. For example, you can overlay area bike maps onto the Google maps view. The site also features local weather and webcam views for selected cities.
The route search feature sort of works, but not that well. If you punch in your U.S. Zip Code, for example, you won't see routes that have been mapped into the area. The site developer, Matt, assures me he's working on it.
Creating routes is similar to those on other sites -- hit the record button, double click waypoints, give the route a name, description and tags and hit 'save.' You can also download GPX and KML files from GPS devices. Be sure to save the URL of the route you created.
Read the help file to get started. Oh, and Matt has a blog.