that being said, another interesting source is just dial (2222 2222) or
www.justdial.com you can get phone numbers for most state roadways offices and they can completely guide you.
An equally naish source is
www.redbus.in They are well worth the money, and even if a bus is not seen on website, you can call them up and they can fix up things for you. Very cooperative and helpful staff. Full marks to them!
Just checked, not a very useful service. Good for someone who already has an idea. Like I know manali-delhi has an AC volvo, but say for recongpeo, i needed multiple tries to figure what class of bus goes.
Like airlines, it should self-select the possible destinations for a given origin (like delhi-shimla, manali, sangla etc etc). again, redbus might be of use where pvt buses go.