My father has the BEST method for dealing with the charities that call soliciting donations. You see, he has been and still is VERY involved with charities in our community over the years, so he knows which ones are legit and which aren't. He will listen to the spiel, and then start asking questions: What was your financial status at the end of the last fiscal year? What sort of investments, if any, does your charity have? I would like more info; can you give me an address and phone number and I will call you back? (he's a chartered accountant, by the way, who used to perform audits on businesses). This usually shuts them up REAL quick and the same one rarely calls back again!
I am never rude, though I realize that for some people this is necessary if you get a telemarketer who borders on militant harassment. I wish they realize that if we wanted the product THAT much, we would go out in person and take care of it instead of trusting some stranger on the phone!!!