Without a doubt, my favorite cover album of the past year (and possibly of all time) was The Bird and the Bee's brilliant Interpreting the Masters, Vol. 1: A Tribute to Daryl Hall and John Oates
I picked one for the top five, so as not to overwhelm. There were plenty of other great covers (you can Google 'em) and here they are:
5. Juniper Tar covering "Via Chicago" on the excellent MuzzleofBees.com compilation Wisco: A Tribute to Wilco
4. Robert Plant covering Low's "Monkey"
3. The Bird & The Bee covering Hall & Oates' "Rich Girl"
2. Cee-Lo Green covering Band of Horses' "No One's Gonna Love You"
1. Bon Iver covering Peter Gabriel's "Come Talk to Me"