I found a website http://www.khanacademy.org/
which has many videos on math concepts. If any of you have any problem in understanding some math concepts. its a useful site. Yesterday I watched videos on probability, premutations, combinations and coordinate geomentry and it was very useful for me in answering GMAT math questions. hope this will be useful to many people.
Please let me know if its unappropriate to post this. I will immediately delete the post.