Jennifer Aniston, Scarlett Johansson and Charlize Theron are among the A-listers who signed on for the Stand Up To Cancer telethon in September. American Idol David Cook, Christina Applegate, Meryl Streep and Sally Field also will appear on the Sept. 5 broadcast, which will be simultaneously aired on ABC, CBS and NBC to raise money for cancer research and treatment. Dozens of other celebrities and sports figures will also be appearing on the program, according to Stand Up To Cancer.