Meritline offers this Canon BCI-6-Compatible Inkjet Cartridge 3-Pack (18 cartridges total), bundled with 20 sheets of photo paper for $18.95. (It's the first option under "Buy More Save More".) Coupon code "MLCS07BN" cuts it to $13.95. With free shipping, that's the lowest total price we could find for the ink alone in this quantity by $9, although we saw it for a buck cheaper last month. It's compatible with Canon i9950, i9900, and i900D printers, among others.
CompAndSave offers its Canon-Compatible PGI-225 / CLI-226 Inkjet Cartridge 12-Pack for $55.99. Coupon code "DEAL225" cuts it to $13.99. Shipping adds $3.99. This 12-pack contains four pigment-based black ink cartridges, and two dye-based ink cartridges each of black, cyan, magenta, and yellow. These cartridges fit several types of Canon PIXMA printers; see the "Compatible Printers" list on the product page for a complete listing. Coupon ends March 10.