I want to implement private cloud for my college using free tools like open nebula etc so where to start? or is there any step by step guide available?
Building you own cloud with Ubuntu : http://www.ubuntu.com/cloud/build-a-cloud
as I have searched and found a very good link about private cloud with Ubuntu.
This a PDF document which will explains you step by step process on setup.
Must read links to understand it in a better - http://www.networkcomputing.com/private-cloud-tech-center/five-steps-to-building-a-private-cloud/240004192