Reusable menstrual pads
Instead of throwing away disposable pads or tampons every month, use washable cotton pads. You can make them yourself or buy them from a number of different retailers.
They can be tossed in the wash with a load of darks, or run under cold water briefly if you're extra concerned.
Think of how many feminine hygiene products you use every month. This is all unnecessary waste! A great easy way to go green is to switch to a diva cup, or similar reusable menstrual cup.
It'll take a little while to get use to it, but once you do it's amazing. Eco-friendly and healthy (no risk of TSS like tampons).