WikiTravel 
Everything you need to know
Agoda.com
The worlds hotels at your finger tips.
good rewards program and helpful reviews
Hostelworld
Great for booking ahead and checking reviews of guesthouses.
Tripadvisor
Great for checking reviews of Accommodation trips and sights
Skyscanner
Flight booking, Great site for finding those cheap fares!
Kayak
Flight Tickets, Another Great site for finding Tickets
Seat61 
Train travel Awesomeness. Rail maps, tips help, info.
Cleartrip
Booking Train Tickets Onlne while in India Excellent
Lonely Planet Forum 
Help from the people who have been there