Question: I guess the title says it all. =) I'm planning to replace my kitchen sink faucet. What type of sealant should I use for the base of the new sink faucet?

Answer: 
Many facuets come with a rubber gasket, so you don't need any sealant, just install the gasket.
Plumber's Putty. Read the manufacturer's instructions just in case. Plumbers Putty is less than 2 dollars at Home Depot so get it just in case (you won't be out much money either way).