Hi, I was in US on L1 Visa for 5 months from 1st May 2010 till 1st Oct. 2010. I have W2 form from my employer. I have SSN.
My wife and son visited me for a month in US on L2 Visa. Now I want file US tax return. I do not have SSN for my wife and son.

I am in India now. How can I file the Tax return?
How can I show my wife and son as dependent?

You can only file nonresident tax return. You can not claim your wife and son. Your U.S. Tax Return: The U.S. Visas (http://taxipay.blogspot.com/2008/08/us-visas.html)

You can deduct transportation, lodging and meals for yourself (not for family). Use Form 2106 or 2106-EZ to figure your allowable expenses that you claim on line 9 of Schedule A (Form 1040NR).