Google Maps...

...have added cycling routes to their motoring, public transport and walking routes.

The option appeared today (unless I'm particularly unobservant and missed it yesterday )

Just don't try using it for the Olympics 'cos a load of them are shut.

It's good to see but needs a work, it shows national cycle routes which are almost useless for anyone other than a day tripper with little luggage and lots of time but doesn't show some of the better approved routes in London.