US State Department PASSPORT INFORMATION website is: http://travel.state.gov/passport/passport_1738.html
For a first time passport the cost is $110 + $25. You need to fill out a DS-11 form. You must also apply in person at U.S. Post Office that processes passport applications or local Passport Agency (using a passport agency costs an additional $60 expedite fee)
For an adult renewal passport the cost is $110 + $12.72 for overnight delivery to get the passport back to you. You will need to fill out form DS-82 and send that in along with your expired passport to:
National Passport Processing Center
P.O. Box 90155
Philadelphia, PA 19190-0155
Please keep in mind processing times for both first time and renewal passport services could take anywhere from 4-6 weeks.