PayPal has a "Sweetest Deals of the Season" promotion, which include cash-back deals with several merchants.  To make it easier for you, here is a consolidated list of noteworthy ones. Keep in mind that the terms are different for each merchant.  Please make sure you review and understand the terms before purchase.

• 1-800-Flowers: $10 cash back on $59 or more with promotion code PAYPAL8
• Abt: $20 cash back on $200 or more
• American Eagle Outfitters: $20 cash back on $125
• Blue Nile: $20 cash back on $50 or more
• Buy.com: Save $5, $10, $15, $20 or $25 with PayPal instant rebates on select items
• CompUSA / Tigerdirect: $20 cash back on $200 or more
• eBags: $10 cash back on $50 or more
• eToys: $10 cash back on $75 or more
• Gaiam: $20 cash back on $100 or more with code PAYPALCB8
• Omaha Steaks: 20% cash back
• RitzCamera: 10% cash back with some exclusions