Applying for Canadian PR while you are in USA ( or in any other country) on thier visa is not an impediment.
You have not mentioned in which category you want to apply for PR in Canada. Any how here is the link for CIC where you can choose your own and decide:
http://www.cic.gc.ca/english/immigrate/index.asp
If you need any more guidance, don't hesitate to make your post in this Forum.
You can apply for a Canadain PR while in the US. However, you have to be in the counrty for more than a year for your application to be processed in the U.S. Otherwise, they will transfer it to your local visa office. Estimated time for processig is from 8 to 12 months. Visit the Canadian immigration website for more information.
I was on L1 while I applied, we applied after 1 year had passed in US. The only thing that you need to take care of is a correspondence address, we applied through a lawyer so all our correspondence was routed to them in Canada.
Actually as per my lawyer, the concept of 1 year in a country is a little misinterpreted. When I approached them, after reading the 1 year condition he told me that I need not have to wait for 1 year if my visa was stampled for more than a year.. assuming that he is correct you may not have to wait for 1 year term...
