I loved Kelly Clarkson from the beginning...I have both her cds, Breakaway and My December, I have to admit the last one is not all that great. I also bought Tamyra Gray's cd from season 1. I've been meaning to buy Carrie Underwoods cd from Season 4, just haven't. I have Chris Daughtry's and Elliot Yamin's cds from Season 5, thought about buying Katherine McPhee's cd but haven't. I am going to buy Jordin Sparks cd. And I will definitely buy Josiah Leming's cd when his comes out, (he didn't make it past Hollywood week this season) he just recently signed with WB. I really liked his voice and have listened to the songs he has written on his myspace page.
http://www.myspace.com/josiahleming