Plants
Plant a garden on your desk
Well, not really a garden, but a small tree or plant for your desk would be nice. Not only will it look nice and probably make you smile a little more, but it will help reduce the indoor air pollution by cleaning up the air you breathe.
By choosing plants for the office you can greatly improve the air quality for you and others. If you bring a plant to work them maybe some of those around you will do the same. In fact, you could help your co-workers by encouraging everyone to bring a plant for their own desk.