Casual browsers would be able to type in their city and search. They could search for ride groups, events (stuff that happens on a specific date such as meetings, classes, political stuff, jams), or routes. If you look at routes, you can see the start points on a map like businesses, and they'd be rated by other users. You click on a highly rated route. On the route page, you would see the Google Map overhead route, the elevation profile (with grade %'s), and notes along the route. The route description would be like a Wiki edited by the community. You could click on points along the route to read user comments or see user pictures. If you scroll down you could see member comments on the route with their review rating. You could see if your friends had done the route and what they rated. If you were a member you could also see your own training history on the route - if you'd done it, and possibly a chart of previous speeds (maybe more data if you uploaded from your bike computer). On the side you could see a list of similar routes, like "people who liked this also liked ...". From each person's review of the route you could click on them and visit their blog, see their groups, etc.
Regular members would update the wikis of route descriptions, add new routes (with the simple Google Map style clicking of end points and dragging mid points), rate routes, track their training, track what rides they're doing. In addition to the route pages, you could view your ride history in a calendar format, which would also show upcoming events or group rides you were signed up for. From the calendar you could also graph things like your speeds and weight over time. You could also have your own blog page. You blog page would include the reviews of routes and events that you write, and also any other blogging about your riding that you want to do.
You could connect with other members and see what rides they're doing and what they recommend, send messages to each other, etc. ala Yelp / Myspace / etc. Of course there would be a forum. People would upload pictures taken along routes. Pictures could go into their blogs and also into the route pages. Of course people would want to take pictures of their rides and use their bike picture as their avatar.