Valrhona is consistently terrific, but watch out for stores which do low volume, as their storage conditions may be sub-par (white blooms, dry texture, bad mouthfeel). Callebaut makes a nice dark bar, which can be hard to find. Michel Cluizel is nice. Fot those liking different tastes/flavors, try Dolfin (the saver pouch is a good touch). In Paris, I have always enjoyed Jean-Paul Hevin.

Truffles? The Woodhouse recommendation (St. Helena, Napa Valley) is spot on: they are wonderfully made and presented, and will show those who still think Godiva is chocolate know the real thing ;-) Teuscher champagne truffles and fresh Maison du Chocolat are way up there too.