I don't believe in Santa and refuse to lie to my child about it. The first year he could ask about it was when he was 3 and I just said that lots of people liked to believe in Santa but really he was just pretend.
I have yet to find a single person who has done the same, even if I can get them to agree in principle, no one will agree in practice. I'd love to hear what others think (other than that I am a Scrooge) and see if anyone agrees with me....