The Lost Lords of Time: Recons Volume One – A 438 page e-book detailing the process and history of reconstructions of classic who episodes.
A Brief History of Time (Travel) – An in-depth website featuring an overview of each season of Doctor Who and in-depth production notes for each serial/episode.
Official BBC Page on Classic Who – Exactly what it sounds like. The page is archived at this point, but they have some cool stuff here. For each serial they have scans of official production pages that indicate, for example, where music was needed to put in to the episode, and where stock footage was taken from, if any.
Doctor Who Wiki – This is the wiki we use (and mention) every week when recording. We don’t read off of it for our summaries, but it’s usually helpful to have it open for production information and air dates, as well as any other cool facts that people notice that we can mention in the episodes.