Hi... I'm on L1 visa here at US for the past 2 years and I got married last June '09 and my wife joined me here by July on L2 visa. She has got her SSN. She is not working now and did not work earlier. She does not have any W2 or other tax related documents as she had never worked here in the US. So, what should be my Tax filing status - 'Married filing separately' or 'Married filing jointly' ? Also, is there any other forms to be filled if we are filing jointly since she is here for the past 6 months only? Please advise. Thanks

You can file joint return or file as married filing separately. It is better choice taxwise to file joint return.
You must both report worldwide income on the tax return.