I got introduced to Helen Cann's work via twitter the other day and was immediately side-tracked by her crazy detailed hand-drawn city map of Brighton (see above). It gets better, visit the map on her site and it comes complete with rollovers from both a local and personal history of all the nooks and crannies in the town's streets and avenues.
Also as immersive (and impressive) is the drawn map she did of the history of coffee houses that began in Exchange Alley (London), starting in 1652. Once again, you can rollover most anything on the map for detailed captions that are sometimes informative and sometimes quirky.
Helen's work is a beautiful nod to the analog world, as it's "...entirely hand produced, mainly in watercolour, coloured pencil, graphite and collage." I'm especially in love with this time-lapse video of her painting up Youthtopia.