I haven't used this website fully or exhaustively yet, and fear that is could turn up dodgy and dingy pubs. But the idea, at least, is fantastic.
It'll randomly choose a pub for you and you can limit it to local areas within London. On the 'coming up features' list are a random pub crawl generator - I'd like to able to give it limits of a theme, perhaps searching on keywords within the description.
People are encouraged to give reviews and I may well join in. I also encourage you to review your local or favourite pubs to help lift this site into a trully useful compendium of London Public Houses.