This Footprint Calculator is a short little animated quiz to determine how many Earths you need to support your lifestyle. It will ask a series of questions to determine your Ecological Footprint, how much productive land and sea is needed to support your activities. Once you finish, you'll be met with some ideas for reducing your footprint.
As with any calculator, this one doesn't address everything. It does not mention composting or cloth diapering, buying second hand. But, I think a calculator that does address all issues would be one long quiz to take! Regardless, I came up with needing about 3.9 Earths.
The Earth Day Network website is full of information. Take some time to browse the site and learn. Sign the Climate Petition and see other ways you can become active to save our Earth.