Best Hollywood Beach Bums

Hayden Panettiere shows off her toned tush while vacationing in southern France with boyfriend Steve Jones. <a href="http://x17online.com/gallery/index.php?tab=by_celebrity&celebrity=Hayden+Panettiere" target="_blank">MORE: Click for extra pics of Hayden Panettiere at x17online.com.</a> (X17)

Jaime Pressly shows her post-pregnancy bikini bum on the beaches on Mexico. <a href="http://x17online.com/" target="_blank">MORE: Click for pics of Jaime Pressly and other fun celebs at x17online.com.</a> (X17)

Pam Anderson proves her bottom is still in Baywatch shape. <a href="http://x17online.com/gallery/index.php?tab=by_celebrity&celebrity=Pamela+Anderson" target="_blank">MORE: Click for extra pics of Pam Anderson at x17online.com.</a> (X17)

Avril Lavigne reveals a hot bikini booty while frolicking in the ocean in Malibu. <a href="http://x17online.com/gallery/view_gallery.php?gallery=ALavigneBeachEXCLU0525_X17" target="_blank">MORE: Click for extra pics of Avril Lavigne at x17online.com.</a> (X17)

Reality star Kristin Cavallari shows off her bikini bum in Miami. <a href="http://x17online.com/gallery/index.php?tab=by_celebrity&celebrity=Kristin+Cavallari" target="_blank">MORE: Click for extra pics of Kristin Cavallari at x17online.com.</a> (X17)

"90210" star Annalynne McCord flaunts her flawless backside on Miami Beach. <a href="http://x17online.com/gallery/index.php?tab=by_celebrity&celebrity=Annalynne+McCord" target="_blank">MORE: Click for extra pics of Annalynne MCord at x17online.com.</a> (X17)

Britney Spears' Circus tour has her bum back in top form. <a href="http://x17online.com/gallery/view_gallery.php?gallery=BSpearsBikini052009_X17" target="_blank">MORE: Click for extra pics of Britney Spears at x17online.com.</a> (X17)

Chloe Sevigny revealed her shapely posterier while vacationing in Miami. <a href="http://x17online.com/gallery/view_gallery.php?gallery=chloe-on-the-beach-20081117" target="_blank">MORE: Click for extra pics of Chloe Sevigny at x17online.com.</a> (X17)

Paris Hilton flaunts her rear end at the swimming pool of the Eden Roc Hotel at Cap d'Antibes during the 62nd Cannes Film Festival. <a href="http://x17online.com/gallery/view_gallery.php?gallery=philton051809_X17" target="_blank">MORE: Click for extra pics of Paris Hilton at x17online.com.</a> (X17)

Audrina Patridge shows off her rear end in Vegas. <a href="http://x17online.com/gallery/index.php?tab=by_celebrity&celebrity=Audrina+Patridge" target="_blank">MORE: Click for extra pics of Audrina Partridge at x17online.com.</a> (X17)