So people keep mentioning their favorite cookbooks under the cooking gear thread, so I figured why not just start a new one where everyone can tell about all those wonderful recipe collections we just have to own:
Pei Mei's Chinese Cookbook Volume 1: The single best Chinese cookbook I've ever found; incredibly authentic and amazingly tasty. Most of the recipes are even fairly fast/easy, though you'll probably need some new ingredients.
The Border Cookbook by Cheryl and Bill Jamison: a wonderful collection of border food recipes which are all fantastic. My burrito recipe that I posted started life as one of their recipes before being mutated beyond recognition. They also have excellent cookbooks on both grilling and smoking, though I don't have the names off the top of my head.
The Indian Menu Planner, Roli and Janssen BV 2002: The cookbook that really got me started on Indian food. Just another good authentic cookbook.
The African and Middle Eastern cookbook, Josephine Bacon and Jenni Fleetwood: This actually isn't where I've gotten most of my middle eastern recipes, but it has a lot of interesting food that I largely hadn't been exposed to before. This is one I actually need to get back to, because I haven't done enough with it.
The Cuisine of the Rose, Mireille Johnston: A great cookbook for classical French cooking, mostly from Burgundy and Lyonnais (she has at least one other for another region of France).
The Foods & Wines of Spain, Penelope Casas: Everything in this cookbook is to die for, and from what I've seen of her other works Penelope Casas is pretty much the authority on Spanish food.