When you're going green you can't be afraid to talk a little trash or to talk sh!t, so lets get to it. The conventional toilet is not very environmentally friendly. New low flow toilets, dual flush toilets and grey water systems can help reduce water waste but there's another kind of waste happening when you flush the toilet... you are wasting valuable human waste!
Through composting this nitrogen rich refuse can be turned from sewage into a great fertilizer. The solution is a humanure dry toilet which can easily be made at home from a 5 gallon bucket, a milk crate and an old toilet seat. Basically, after you do you business you cover it up with a layer of non-toxic sawdust. Once the bucket is full you dump it into your (hopefully outdoor) humanure pile and compost at high temps for a year. You end up with a great fertilizer so you can shout "from whence you came" as you fertilize your garden.
The good folks over at Homegrown Evolution provide a great tutorial on building your own humanure toilet. They acknowldege that composting your own feces is still a controversial topic that understandably makes people a little queasy, but point out this can also be a great solution for a camping toilet. So whether you are ready to take the plunge and go hardcore green, or you need an emergency toilet for your remote wilderness cabin check out this cool tutorial.
You may also want to read up on Humanure and Composting Toilets over at the Humanure Handbook.