Creating a thanksgiving brine for a 7-8 lb Turkey?
Alton Brown uses 1 cup kosher salt and 1/2 cup sugar for 2 gallons of liquid (1 gallon ice water, 1 gallon vegetable stock).

You can reduce the amount of liquid to whatever you need to immerse the turkey in liquid. So for 1 gallon of liquid you would use 1/2 cup salt and 1/4 cup sugar.

The answers in this question recommend a brine that is 5-10% salt by weight (comparing salt to liquid).