Office Paper Systems has a facility at 7650 Airpark Road in Gaithersburg (take Shady Grove Road past Muncaster Mill Road, and it becomes Airpark Road) that accepts paper that needs to be shredded. You can bring your materials in boxes, plastic garbage bags, whatever. If you have huge volumes, give them a call first so that they are ready for you.
This is a free service. OPS will recycle the shredded material, so you are securing your identity and recycling paper at the same time! The website is www.freesecureshredding.com.