Dell has launched an "InkSave" program, where consumers can return used ink cartridges for an automatic replacement.

The model seems similar to that used by Netflix, where customers return movies using a prepaid envelope, and receive the next preferred movie on their list.

InkSave is similar: Dell's printers ship with a pre-filled ink cartridge installed, and a spare. When the original ink cartridge is exhausted, the Dell customer simply returns the original cartridge in the prepaid envelope, and Dell sends the customer a new one. The customer is automatically billed for the new cartridge, a Dell representative said in a blog post.

Users can sign up for free on the Dell Web site. After doing so, Dell will send a welcome kit with an ink cartridge and the envelopes. 

EDIT 8:48 AM PDT: It's worth noting that HP specifically does not include envelopes to recycle its ink cartridges. In part, that's because the company does not offer a program similar to what Dell offers. HP does recycle cartridges, however, but you will need to take them to an authorized location, such as a Staples, where you can buy another cartridge.

Transitioning the HP Planet Partners program from envelopes to authorized retail recycling provides more convenient opportunities for customers to recycle HP print cartridges and reduces the amount of shipping material required for recycling returns. Many customers already bring their used cartridges to retail stores when purchasing replacement cartridges, so offering HP print cartridge recycling at Staples stores offers an added convenience for them. In addition, cartridge collection at retail recycling locations has the potential to improve transport efficiency, as cartridges collected at retail locations will be transported in bulk to HP for recycling.