I would be traveling to Philadelphia (PA) from India on work for 9-12 months. I would be paid by the US counterpart of my co. ~$4,000 per month (in the form of daily allowances). I'd however continue getting my salary in INR back home. My wife and kid plan to join me in 2-3 months' time. We'd be obviously renting out a flat and lease a car.

Can you please help me figure out the Fed tax rate and amount that would be applicable for my family? Any specific weblink that would help me with the legwork on US Tax rates applicable for H1B visa holders from India?

Thx in advance.

Your income in the U.S. on H1-B is taxable and is also subject to Social security and Medicare taxes.

You can file jointly with your wife and you both CHOSE to be treated as resident aliens. This will allow you to claim the $10,700 joint standard deduction plus two $3,400 personal exemption (for yourself and your wife) plus one $3,400 for your child PLUS the $1,000 Child Tax Credit.

The downside is that you must declare ALL 2007 world-wide income. There are two offsets available, by either claiming a Foreign Tax Credit (Form 1116) or a Foreign Income Exclusion (Form 2555).

Even with the downside, this is probably the best way for you to file.

You can file joint return as married only after you complete substantial presence test.
Read Your U.S. Tax Return: Substantial Presence Test

For more info on foreign income and form 2555 and 1116, Read:
Your U.S. Tax Return: U.S. Citizen or Resident with Foreign Income