Ricky Skaggs and Nickel Creek would be my two current faves, though my bluegrass collection is admittedly thin (though hoping to grow significantly). Being a fan of a huge variety of music, I am always amazed at how involving good bluegrass can be. He's not bluegrass (and in fact he's hard to characterize), but while looking for new bluegrass material, I stumbled onto Bob Wills (the King of Country Swing) a few years back. His music involves some elements common to bluegrass, and his music puts a smile on my face like none other.
Tom.
Tom.