Staples is offering three dollars in Staples Rewards toward a future purchase of ink or toner when you bring in used ink cartridges from HP, Lexmark or Dell printers. are returned to their retail stores for recycling. Staples also offers a service they call "InkDrop" that makes it easy to get a replacement ink tank, as long as you're not in a big rush. With InkDrop, you mail back an empty cartridge using a prepaid shipping pack, and Staples sends you a replacement with free shipping. They claim that as many as 500 types of cartridges are available via InkDrop.