I like organic, fair-trade chocolate, especially the stuff made by Equal Exchange.
http://www.equalexchange.com/chocolate-bars
I get them at my local food co-op.
For cooking, I liked to use Scharffen-Berger, but I've become suspicious of their products since they were bought by Hershey. So now I use Ghiradelli. And Will, I am so with you on the Ghiradelli sundae...every time I get to Ghiradelli Square I have a hot fudge sundae.
My favorite European chocolate would have to be Droste, particularly the orange-flavored pastilles. My family's Christmas tradition was to get a Droste chocolate orange and a Droste chocolate alphabet letter (usually one of our initials) in our stocking.
http://www.droste.nl/data/content/engels/index.php