The exam pattern for IIT JEE has changed from 2013. You need to score above 80% to be eligible to appear for the IIT JEE entrance exam. In addition, you need to take 2 separate exams to clear it.
NIT will also accept IIT JEE score, while IIIT, which earlier accepted AIEEE score, will also accept IIT JEE because AIEEE has been merged with IIT JEE from 2013.
There are many private universities where you can take admission through the entrance test conducted by them separately. We suggest that you go through their websites individually to find details.
Here are some relevant articles that might help you:
IIT JEE Mains Entrance Test-2013 on New Format to be Held on 7th April 2013