I love this site! Bruce Scottow a.k.a. the Tour Master has laid out a dozen or so in-depth walking tours in L.A. - for free! The tours are extremely detailed and well organized and most offer various side trips that you can choose to add to your tour or not. It focuses on encouraging people to take mass transit to and from - and often during - the tours. All the main tours have a hsitory section as well as lots of fun quotes and facts along the route.
The site is constantly evolving and being updated so check back often. Maps are slowly being implemented into each tour and side trip and next Bruce is working "where to eat" tips and a what's new section is up and coming to keep you in the know.
This site is also built in wordpress to allow for easy updating.