Rates would be averaging abt Rs 7-10 ( USD .20 -25 avg)depending on phone compnay and plan..but mostly for US calls u get prepaid calling cards which give great value ( I believe arnd USD.10 per min approx)..
Check out the sbelow sample links of some telecom operators..
http://www.vodafone.in/newusers/whyv...d.aspx?cid=hyd
http://www.airtel.in/wps/wcm/connect...Calling+Cards/
http://www.rcom.co.in/Rcom/personal/...=USCanadaCards

There are many other operators also like Aircel, Idea Cellular etc.. but the above will give u a good idea of the rates..

Cheers
Abhi