Hostelworld is a great app for hostel options. Easy to use, great overview of available accommodation, reliable and offer some amazing and unique hostels.
For cheap and good options try booking.com else an app known as Agoda. I booked hostel and homestay through both during my last trip to Rajasthan this feb end.
There are various of apps who can help you with your desired backpacking hostels and home stays with .. still my first choice is always zostel .. because their the ambience is something which always cheers my mind up .. and the app which I use is Booking.com ... Have a great day !!