What should I use to lubricate a freehub? I've noticed my freehub has gotten quite a bit louder over the last few months. Several people have recommended that I lubricate the freewheel by tipping the bike on its side and dripping lubricant into the freewheel. However, I've gotten differing opinions on what to use for a lubricant.

Is it safe to use a chain lube on the freehub or is there a better lubricant for this purpose? 

Edit: In response to one of the answers, I have a freehub (2011 bicycle). Question edited appropriately.
Freewheel (old technology) or freehub (current technology)?   People tend to use the terms interchangeably, but they are quite different. 
A freewheel can be pretty effectively lubed with any medium-viscosity oil.  There's not much in there; a couple of ratcheting "pawls" and their pivots.  

You don't want anything that will gum up and cause the pawls to stick.

On a freehub, the mechanism is pretty well-sealed and greased from the factory.  However, they are pretty easy to disassemble in most cases.
They do make a clever tool called the "Freehub Buddy" which lets you inject grease into the thing without disassembly.

However, at 40 bucks it's a bit steep for home use where you would only use it every couple of years or so.