Commenter Der Bingle rightly mentioned here that The Puppini Sisters did a great version of Elton John's Step into Christmas. Full disclosure: I did not know Elton wrote that song (nor that he wrote another Christmas-y song, here). The flipside to Step into Christmas (Who'd be a turkey at Christmas?) was probably written in 3 seconds, yet it's quite funny. Step into Christmas was covered many times, and usually pretty bad. But these rockin' versions by London skinheadband The Business and indie darlings The Wedding Present are good.
Elton John - Step into Christmas
Elton John - Who'd be a turkey at Christmas?
The Business - Step into Christmas
The Wedding Present - Step into Christmas (link = fixed)