One of the best ways to travel in Europe is by train, they go everywhere in Europe from cities to small towns. They are safe and clean and one of the fastest way to cover many places in shortest possible duration. Raileurope provides you with passes to travel within a country or a region. Do check their seasonal deals. You can buy the pass online or can contact travel agents like Thomascook who at times can give better discounts on the pass. Besides the rail pass you may also receive some deals and offers provided by their partners.
Places where planes can’t reach, trains don’t go or have odd timings, that where the only cheap travel option remains is bus and in India red bus is one option I know and use.
For self drive car rentals in India. You can drive on your own or even take a chauffeur if you prefer. Drawback is that it provides car rentals in major cities only as of now. You can take it anywhere ofcourse. Rentals by hour,days or months. And their prices do include the fuel charge.
Kayak is for both cheap airfares as well car rentals. They search hundreds of car rental website and guarantee lowest prices/deals in car rentals. They work with leading brands worldwide and there is free of charge amendment on car bookings if required.