Resources that explain the science of cooking?
IMO, this really would have greater lasting value with a single detailed answer instead of a poll.  Here's an annotated list of all the recommendations so far:


On Food And Cooking (Harold McGee) is all science at a very detailed level, combining food chemistry and biology and explaining the interactions between ingredients and the mechanisms behind various cooking methods.  If you're looking for a pure science book, this is it.
Good Eats: The Early Years and Good Eats 2: The Middle Years by Alton Brown.  His books are less technical/scientific than other authors and tend to focus more on application, making them more accessible to less hardcore cooks.
CookWise (Shirley O. Corriher).  Written by a biochemist who has done a lot of consulting in the food industry.  This is more practical than McGee and more technical than Alton's books.  It also includes a ton of recipes, which can be a good thing or bad thing depending on your personal preferences. She has also written a baking version, BakeWise.
Molecular Gastronomy (Hervé This, translated by Malcolm DeBevoise).  This is more of a niche book (about - surprise - Molecular Gastronomy) and as you might expect is a little French-centric.  What's really great about this book is how it debunks a lot of popular cooking myths with actual controlled experiments and hard data.  It wouldn't be my first choice to recommend to a Food Science newbie, but nevertheless a good one to add to your collection.
The Fat Duck Cookbook (Heston Blumenthal).  Written by the founder of the Fat Duck Restaurant in the UK.  It's about the history of the Fat Duck and has a big recipe collection (from the restaurant, obviously) and a section at the end dedicated to food science.  This one's really for the advanced crowd as it involves a lot of molecular gastronomy, sous-vide and other esoterica - complex preparations, hard-to-find ingredients and unusual/expensive equipment.
Cooking for Geeks (Jeff Potter) is, as the title implies, written to appeal to geeks, and as such has a certain amount of science but tends to be quite a bit more basic as far as actual cooking technique goes.  It's more "applied science."  Honestly, I wouldn't recommend this for very experienced cooks, but it's great for getting into cooking and gaining an enthusiasm for it (if you're kind of a geek).
Cooking for Engineers is a web site, not a book, which has the obvious advantage of being free and searchable.  It's hard to really define this as its scope is so wide, but I will say that I've found it to be a surprisingly useful and detailed resource whenever I need to find out something quickly.
What Einstein Told His Cook (Robert L. Wolke) is also mostly on the science itself but is written to be more accessible to the layperson.  As one reviewer on Amazon put it, Wolke is like the Bill Nye of Food Science.  One part science, two parts entertainment.  Another member has criticized it for making unproven claims (particularly on nutrition).
The Cooks Illustrated annuals (from America's Test Kitchen) are less about the actual chemistry of food but do highlight a very scientific approach to cooking based on up-front research, experimentation and testing.  See David LeBauer's Answer for a more detailed explanation.
The Science of Cooking (Peter Barham) focuses on the chemistry and physics of why some recipes work and some fail.
khymos.org - on the surface it's about molecular gastronomy, but you'll find much of the science of cooking (e.g. the chemistry behind "working" flavour pairings etc) on there too.
The Food Lab: Better Home Cooking Through Science (J. Kenji López-Alt) is a collection of detailed recipes, tips and explanations.  It's written to be easily accessible to a chef without much experience.
Serious Eats is a website with both recipes and stories about how the recipes were developed (often with pictures of various attempts to compare how changing processes or ingredients affected things).  Especially see the 'techniques' section of The Food Lab