The postal rate for a regular letter is

49¢

The rate for a postcard is

35¢

These rates took effect May 31, 2015.
In January 2016, USPS increased some postal rates, but not these.

Owing to the dispersion of Forever Stamps, and USPS.com now surfacing this information no more than one page deep, this will be the final update to The Postal Rate. This site will be taken down the next time rates change.