Hi

I got married this year and my wife is still in Pakistan. I will not be applying for her Green card until next year when I become US citizen. Would I be able to file my 2011 tax under "married filing jointly" category? She doesn't work and has absolutely no income. What kind of identifications do I have to show for her? Do I need to also provide our marriage certificate (translation)?

Thanks
Imad

If you are a resident alien/permanent resident you can choose to treat your wife as resident alien for tax purposes. You would need to add a statement about this choice to your tax return including both your names, addresses, SSNs or ITINs and both of you must sign. Than you can file as married filing jointly.
You would need to apply for an ITIN for her if she is not eligible for an SSN. To apply for an ITIN use form W7.
Have a look here how to obtain an ITIN from abroad:
http://www.irs.gov/businesses/small/international/article/0, id=96690,00.html

I know this is what I would normally do if she was here. But can I still do this although she has never been to US and I have not applied her green card yet (as I said I'll do that next year when I have my citizenship). Thanks for your help.

Yes you can. Look at the link I provided.
There it says for example:
Thus, in the case of an individual who lives abroad and who is filing Form W-7 with the IRS to apply for an ITIN, instead of attaching his/her original passport, national identity card, birth certificate, etc. to Form W-7, he/she can attach "copies" of these documents to Form W-7 accompanied by an apostille properly signed or sealed by one of the appointed competent authorities of his own nation. A model apostille may be found at: Apostille. In addition, refer to Apostille Section.