I'm not sure who rediscovered it first, but thanks to everyone who's linked to it so far including Fast Co. Design, Creativity Online, Wired UK, PSFK, Roomthily, Inteloquent, OpenStreetMap and numerous Twitter and Facebook users.
The map has been picked up by a few books and exhibitions over the years, including the wonderful Form + Code by Casey Reas and Chandler McWilliams. If you're interested in how this kind of work gets made then the book is essential.
If you're interested in a more thorough theoretical exploration of isochrones I can recommend Nicholas Street's Time Contours paper on the subject. If you find yourself yearning for an even deeper treatment of transit data, look around for people like Mike Frumin who take research far more seriously than I do!
If you want to play around with this code for yourself, it should be relatively easy to fix up for current versions of Processing (probably just the fonts will need updating, please leave a comment if there's anything else) and you can get the data here.
I've had a few requests to update the map with current data, including the East London Line and Heathrow Terminal 5, as well as suggestions to include the overground in south London and elsewhere. Sadly I haven't found a coherent and consistent data source that I could drop-in as a replacement for my hand-edited original. The official Transport for London data sources on data.gov.uk look promising, and I've had a couple of under-the-table offers from people with access to time-table data, but these all require more time and effort than I have for the map at the moment. In future I'd like to move the map to a more 201x format like Canvas or SVG, perhaps porting to Processing JS. Perhaps an app? One day...