From Wikipedia:

"Gimme More" was the first single from Blackout. Spears performed the song at the 2007 MTV Video Music Awards on September 9, 2007. It was released earlier to radio stations on August 30, 2007 and as a digital download on iTunes on September 27, 2007. "Gimme More" became Spears' highest peaking single since "...Baby One More Time," having reached number three on the Billboard Hot 100. Since the release in September of 2007, "Gimme More" has been certified platinum in the U.S.