Check out this website
A Song of Ice and Fire
Some of the castings are great (e.g. Doran Martell=Ciaran Hinds , Oberyn Martell=James Purefoy, two of the actors from Rome)
some of them are wishful thinking.
But you'll enjoy seeing who 'they' (from the AsoIaF board) have chosen.
E: LOOL!! they've got Matt Lucas as Varys!