This is the official website for the David B. Gamble House. Here, you can find quite a bit of information concerning the house, it's architecture, its architects, as well as other tidbits. There is even a virtual tour that's worth checking out, especially if you don't have the time to visit the house itself.
The Greene and Greene Virtual Archives
This is an impressive website that hosts images and photos of the Greene brother's famous works throughout their lifetime. Besides having the Gamble House featured here, there are also examples of churches, other houses, and furniture that the Greenes designed themselves. A great place if you're looking for a specific piece from a specific time period.
This is an amazing book that showcases images of the Gamble House that you wouldn't normally notice even if you attended the tour of the house itself. It boasts an impressive historic background reference, and features hundreds of pictures of the house. There are even photos of the most miniscule details.