Now I am involved in collecting pens, Sharpie Markers and Highlighters from work when they get dried up. It's an easy system and you can raise money for your favorite charity. What I like about Terracycle is that you can print a pre-paid label and shipping the items doesn't cost you anything. A lot of recycling programs can get expensive because they don't cover shipping expenses.
It's really easy to get started and register. And besides writing instruments, they collect all sorts of packaging that normally can't be recycled. So you might want to check out their website to see what things you can contribute.