I want to work on NVIDIA GPU cluster for my thesis. But the cost of clusters are too high for me to bear. Although I can buy a couple of latest GPU cards, but buying cluster is impossible for me at least right now. What is the alternative? Are there any Non profit organization promoting and renting clusters for educational purpose at subsidized pay per use rate?
If you work at an institution in the US or have collaborators at one, you should look into the XSEDE program. This is a federation of the National Science Foundation funded supercomputing centers in the US which provides compute cycles on a variety of large-scale machines to open science research in the US. There are a couple of machines with GPU resources including Keeneland and Stampede.
Startup allocations are readily available to academic researchers and can be applied for on the XSEDE User Portal. As a student researcher, you will need to work with your academic/thesis advisor to get them to apply for time. If your application for an allocation of time is successful, the time itself is free.
A final alternative is to rent (or apply for time on) a GPU cluster from Amazon EC2. As Bill and others have mentioned, most countries provide some national or regional high performance computing resources for free to their scientists. If you don't have one in your area, it is mostly a matter of finding a collaborator who does.