Google maps is a great starting point. I've stopped using Bikely and Mapmyride at all, and now use Google's bicycle directions to plan my routes, and my GPS when on the road supplemented with paper maps.

When you come across bike paths not on the map (or get routed onto streets inappropriate for biking, I'd suggest using the "report a problem" link on each page to tell them. I do this fairly often, and Google does fix these problems.