At the moment, there are three stackable promotions running on Keurig coffee makers at Staples. Each promo is effectively 20% off the original price. First is a 20% off coupon (linked below). Second is a Staples easy rebate for a Staples gift card in varying amounts ($20 for the B30, $25 for the B145, and $50 for the B155). Third is a mail in rebate from Keurig (PDF linked below), also for varying amounts depending on the model ($20 for the B30, $26 for the B145, and $50 for the B155).
Thread for 20% off one item
Keurig Manufacturer's Mail in Rebate [keurig.com]
Product links (for reference only...coupon is only good in store)