15th March 2010: A Science Diet cat food coupon or a $5 discount is available at this time. This is a USA promotion only, it seems. You have to register first as usual. The link is: http://www.hillspet.com/natures-best/natures-best-discover-feline.html
The product, though, is Natures Best®. Not sure of the difference (if there is any difference!)
Also on this date there is a £5 voucher for Hill’s Science Plan Pet Food available if you register. This is the linked page:
Also on this date and on the same page there is a chance to win free pet food for one year.
And on this day MEVIO are offering a 10% discount voucher from Petco (USA) on this page:
LINK BROKEN 2012
I don’t know if this is still available but it is still on the internet at this time:
Hills 3 bag challenge. Buy three bags and get a discount with “valuable coupons” and a FREE pet kit!