I'm not sure how these could be "confirmed so early" but here they are anyway.
Credit:The 3 Amigos at PWS and Wikipedia
From Wikipedia:
The 2006 Great American Bash is set to take place on July 23, 2006 at Conseco Fieldhouse in Indianapolis, Indiana.
The following matches are confirmed for the Great American Bash:
For The World Heavyweight Championship: Rey Mysterio (c) vs. Booker T
Winner will recieve a shot at the World Heavyweight Title: Kurt Angle vs. Randy Orton
Mark Henry vs. Batista
The Great Khali vs. Undertaker
In a Street Fight Match: Finlay vs. Bobby Lashley
For The WWE United States Championship: JBL (c) vs. Chavo Guerrero
For The WWE Tag Team Championship: Paul London & Brian Kendrick vs. The Mexicools
Chris Benoit vs. Ken Kennedy