I have been using MapmyIndia website for a long time and they surely have come a long way. It was a basic website with directions and maps, which had a tough time to open up and now they have moved up the value chain and it is improving.
From what I understand they have all the cities, villages, towns, road network mapped out. On top of this MapmyIndia also has lots of data quite relevant to local search(that being said it is nowhere close to justdial.com).
All in all, I like Mapmyindia.com for directions that are turn by turn(some of the road selections should be taken with a pinch of salt) but over-all quite decent when compared to Google maps etc as the content is more detail and more attribution(i.e. more road names etc).
MapmyIndia is fairly popular and they have also gotten a GPS unit, which I have used. I recommend the website and it is quite fascinating to see your anscestral village and towns which you can search. In addition you can get turn by turn dynamic driving directions for all India across all states and cities.
Enjoy browsing.
Shiva