Okay, most of the English links I used to have no longer exist - if you run or know of a good Jekyll & Hyde site, let me know!

The official website: Jekyll & Hyde
The official German site - info about the Cologne production! Jekyll & Hyde - das Musical
A fantastic site about the German production (but in English :-) Jekyll & Hyde - the musical
Another good site about the German version Roman's Jekyll & Hyde page
Another fan site, mostly Broadway stuff Broadway Fiends: Jekyll & Hyde
A fan site for the Cologne production: Jekyll und Hyde
An interesting looking card game based on the story! Dr. Jekyll and Mr. Hyde, the card game