There are several good websites that are of assistance to a rider, here of some of my favorites:
Bikely -- find and map routes
I have tried other route making tools but bikely is the one that I have stuck with. One of the main reasons is that it does not lock up when accessing from work. I like the features of mapmyride better but it seems to always lock up at work. With mapmyride it will create the turn by turn directions for you whereas you have to enter them by hand in Bikely. Another annoyance of Bikely is that I have to do a password recovery every time I need to get to my routes. It does not matter what computer or browser or password, when I go to login it says that my password is wrong. I have searched for others complaining about this problem but have not found anyone else with the problem.
MyCyclingLog -- log your rides and obsess on the numbers
I often laugh at myself that I probably ride 30% of my miles because I am trying to beat some personal record or goal. But hey, whatever gets you out and riding, right?
It also has a section to enter your bikes and track your maintainence. This is great for seeing how many miles you have on a set of pedals or whatever.
Google Maps -- Bikely uses Google maps but there are features that it does not like the terrain and street view. These are great tools to see what hills you are climbing or if lazy like me, find a less steep route. Street view, if available in the area that you are riding, can be used to show if a street has bike lanes, where there might be bike racks and such. Also, with a custom map, I can track which roads I have ridden to make it easier to find an unexplored one.
Twitter -- let people know where you disappeared to
Using Twitter I can post my route and at rest points update how far along I am. This way if I dont turn up home, my SO knows where to look for me. In case I get tired, pull a stupid and ride off the road into a ditch or something. Or answer the 'when you gonna be home?' question.
BicycleTutor -- Maintenance How-Tos in video format
This guy is great and has made a series of videos of hot to perform maintaince on your bike in an easy to follow manner.
Sheldon Brown -- Bike Info God
No list would be complete without a nod to the late Sheldon Brown. Here you can find answers to so many of your cycling questions.
Anyone else have a good web site that helps them?