Chow has an excellent article on sour beers. If you have any interest in the topic, it's a must-read.
Ah, Brettanomyces. My darling.
Soggy Coaster's first experience with a sour beer was The Dissident from Deschutes Brewery. It was something of a personal revelation.
Since then, Soggy Coaster has tried Avery Brabant and New Belgium's Lips of Faith Dark Kriek and La Folie. The Dissident was better than any of those, but any beer in this vein is an exciting departure from the norm.
I think it's about time Ska brewed a Brettanomyces sour. How 'bout it, fellas?