There are a lot of Kristen caps here, thought this would be helpful. If I've missed any or if more are added, please comment so I can add them here!

Movies
Reefer Madness: The Movie Musical (as Mary Lane, 2005)
Forgetting Sarah Marshall (as Sarah Marshall, 2008) (extras: Gag Reel)
Fanboys (as Zoe, 2008) (extras: Behind the Scenes, Interview)
When in Rome (as Beth, 2009) (extras: Gag Reel)
You Again (as Marni Olsen, 2010)

TV
Deadwood (episode 1x07, Bullock Returns to Camp)

Talk Shows
Late Night with Conan O'Brien - April 12, 2005
Jimmy Kimmel Live - November 14, 2005
The Late Late Show with Craig Ferguson - November 28, 2005
The Tonight Show with Jay Leno - July 27, 2006
The Late Late Show with Craig Ferguson - February 4, 2008
The Late Show with David Letterman - April 15, 2008
Live with Regis and Kelly - April 16, 2008
Good Day LA - October 7, 2009
The Bonnie Hunt Show - October 10, 2009
The Late Late Show with Craig Ferguson - October 15, 2009
Lopez Tonight - January 27, 2010