I donate to these guys all of the time (Damn good cause). I haven't tried large kitchen appliances but here is there FAQ's from what I can tell the only things they don't accept is "used baby items". I haven't researched enough to know everything that they do and do not take though.
Purple Heart Pickup Service - What Do We/Don't We Take?
Edit: It doesn't look like they take large kitchen appliances either. They give you a number to call and ask why. If I had to guess I would say that it has something to do with insurance. Say the appliance catches on fire then they are liable...I am merely speculating though.