As of Monday, May 14, 2007 stamps for first-class letters cost $0.41 (first ounce) and $0.17 (each additional ounce). First class large envelopes are $0.80 (first ounce) and $0.17 (each additional ounce). First class packages are $1.13 (first ounce) and $0.17 (each additional ounce). Priority mail flate rate boxes are $8.95 while priority mail flat rate envelopes are $4.60.
For those who want to avoid future stamp price increases, the United States Postal Service has introduced "Forever Stamps" available from the The Postal Store. Also available from The Postal Store is a link to a pdf containing the new domestic and international rate charts.