This is from a prolific contributor to the alt.bbq newsgroup. He has since passed, but his brine lives on, and has drawn many compliments. If you like crispy skin I'd add Cook's Illustrated method to the end.
Hound's Citrus Brine
Prepare the brine:
1 gallon water
1 cup Kosher salt or 1/2 cup table salt
juice of 3 oranges
juice of three limes
juice of three lemons
rinds from same
1 sliced white onion
1 head of garlic, crushed
stems from a bunch of cilantro, chopped
serranos to taste, minimum of 4
rough ground cumin and coriander 2 Tbsp each
1/4 cup chili powder or any ground chile you prefer
(1/4 cup onion powder is optional)
(1/4cup garlic powder is optional)
Place the bird(s) and plenty of brine solution in a ziploc bag(s) and
leave refrigerated overnight prior to cooking. A cooler works fine also.
I use a 5 gal beverage cooler for all but the biggest turkeys. Frozen
soda bottles, or ice can be used to keep the cold. {8 lbs of ice= 1
gallon of water} An hour before cooking take the bird out and
thoroughly wash it down with cold water for at least 30 seconds. You
can place aromatics like garlic heads, apples, citrus in the cavity of
the bird for the cooking. I like also to place orange slices between
skin and meat. This works for either chickens or turkeys.
If you eliminate the brine (salt and water) the rest of the recipe makes
an excellent marinade for grilled chicken.