By Sharon Clott Kanter
Updated Dec 22, 2010 @ 2:46 pm
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Matt Keeble/Splash News and Pictures

'Tis the week for shopping! Some of our favorite celebrities are out and about cramming in some last-minute holiday purchases, including Sienna Miller, who was spotted carrying bags from Heidi Klein and Zadig & Voltaire in London today. See more holiday shoppers, from Jennifer Garner to Rihanna to Reese Witherspoon, in the gallery.