In this recipe, I was generally inspired by Sous Vide Scallops at Believe the Lie, and Twice Cooked Scallops at Ideas in Food.
Here's the short form of the recipe:
Cook scallops with butter, salt, and pepper at 122 F
Chill the scallops in an ice bath
Sear the outside in very hot oil
Step 1: What Is Sous Vide?
My two favorite references for sous vide are Thomas Keller's Under Pressure and A Practical Guide to Sous Vide Cooking by Douglas Baldwin.
Step 2: Sous Vide Equipment
Sous Vide Magic PID temperature controller purchased from Auber Instruments on Ebay
Winco ERC-50 25 cup commercial rice cooker1
FoodSaver Vac 300 Vacuum Sealing Kit
Update: since I purchased my equipment, Sous Vide Supreme has started making an all-in-one unit designed for home use. The regular 10L unit is $400, and the still-quite-roomy 8.7L Demi is $300 - comparison here.
1 A rice cooker or electric kettle can also work; the variables are size of container, and speed of heating. The key is to make sure your heating device doesn't have a brain, as the PID controller works by cycling the power on and off and you can't be resetting your crock pot each time.
Step 3: Vaccum Pack the Scallops and Butter
Step 4: Cook the Scallops
Step 5: Chill the Scallops
The scallops are now cooked, and you could eat them, but to finish and make them a masterpiece, you want to sear both sides.
Step 6: Sear the Scallops
Heat a little bit of oil or butter until it is just smoking, and quickly sear the top and bottom of each scallop. You are aiming to caramelize the surface without further cooking the interior.
After searing (or at the same time in another pan, as my pictures show), heat the reserved scallop-liquid and reduce it. Don't try to reduce the liquid and sear the scallops in the same pan at the same time -- the liquid will keep the temperatures below proper searing levels, and you'll overcook the scallops. The reduced liquid is delicious, and can be poured over the scallops or another accompanying dish.