If you've never heard of menstrual cups, they're the best thing since sliced bread. Really. No, I don't work for one of the cup companies. I own a cup, and I wished somebody had told me about them when I first got my period. Not only would I have saved a lot of plastic from going into the landfill, but I would have also saved a lot of money, and wouldn't have had to deal with that diaper-rash like thing that you get after using disposable pads for a week or so. (They really are like wearing a diaper).
And they're a lot more comfortable to wear than pads or even tampons.
There seem to be more and more companies popping up every day. A couple of years ago, there were only The Divacup (Canada), Mooncup (UK), and The Keeper (US), but now there are the Lunette (Finland), Femmecup (UK), and Moon cup US (Made by the same people as The Keeper).
There also cloth menstrual pads that you wash and reuse. It's really not as gross as it first sounds. I've been using them for over 2 years. They're much more comfortable than disposable pads, and don't create any waste.
As I'm sure you already know, plastic is horrible for the environment. It takes approximately 1,000 years to degrade.
Not to mention the chemicals that they put into tampons.
There are a few companies that make cloth menstrual pads, (Gladrags, Lunapads) and there are also lots of patterns online if you want to try making your own. I would recommend using PUL as a backing if you're going to make your own, so that they don't leak through to your panties.