prompted by the "tesco xmas delivery slots" thread i just signed up for waitrose delivery and found a code that gives £35 off your first 3 orders (£10 off 1st order, £10 off second, £15 off third). minimum spend is £50 per order so i split my xmas order into 3 to get the full discount on it. it reduces the discount a bit as you have to pay 2 additional delivery charges (£5 ea.), but still a decent discount (and xmas slots are currently bookable!).
code is save294, you enter it for the first order and it remembers for subsequent ones. source for the code said it expires jan 31st 09, but since it also said it was a £25 total discount i don't know how accurate that is.
enjoy