The Apple store near me (Woodfield Mall, Schaumburg IL) randomly has a table of returned and/or refurbished products at the back. It doesn't appear to be there on a schedule. Sometimes it's there, sometimes not.
One friend of mine traded his base model MacBook for the middle model. The next week, we saw his old MacBook on the discount table, at something like a 15% or 20% discount.
Occasionally they'll have floor display models for sale. They're complete and tested, but maybe a little more scratched or scuffed, or just plain dirtier, than a typical refurb. Not sure if I'd buy a laptop that's had hundreds of hands on it (picture a kid with a runny ice cream cone playing with a MacBook, and the kid behind him waiting to play on it is blowing snot bubbles). But for an iMac or Mac Pro, the keyboard and mouse are easily replaced.