Just a reminder to sign up for Staples Reward if you haven't done so. Staples Rewards is one of the best rewards programs I've seen. One of my favorite things is that you can turn in your used ink cartridges and earn $2 in rewards for each one. You can then use those rewards towards other products in the store (think Walgreens and RR's or ECB's).
You're allowed to turn in 10 a month and if you have a home business or print an insane amount of coupons (like I do) then that's not all that hard to do. I turn in my used ink cartridges and get the rewards back in the mail in a few weeks. I use that to buy school supplies, office supplies and even office furniture!
Don't throw those cartridges away, take them to Staples and save!