Modest Mouse will be the headlining act for the Sunday portion of the Treasure Island Music Festival in San Francisco on September 16th. Other acts include Spoon, Built to Spill and Clap Your Hands Say Yeah. Thanks to orange4cat for the info.

Source: http://www.treasureislandfestival.com/

The show on August 8th in Brooklyn has been changed to September 8th and the venue has been changed to the McCarren Park Pool. Thanks to Mike for the info