The Old Bailey, online.  Try to picture the staggering amount of information on this site:

“The Old Bailey Proceedings Online makes available a fully searchable, digitised collection of all surviving editions of the Old Bailey Proceedings from 1674 to 1913, and of the Ordinary of Newgate’s Accounts between 1676 and 1772. It allows access to over 197,000 trials and biographical details of approximately 2,500 men and women executed at Tyburn, free of charge for non-commercial use.”

On top of this, there is a great amount of general information, from who lived in London and when and what the different communities were like, what types of punishments were common… just click on the ‘historical background’ link and get into it.