A good basic site to start looking for lightning information. Many links available.
This site is focused on safety. Prevention is the best approach to lightning safety. Read on!
I think this is the best page on the green flash. Andrew is a physicist who studies atmospheric optics.
This page will show you where the latest earthquakes have been, and how strong they were.
A list of active volcanoes with descriptions of activity.
This is the best place for more detailed weather info. A general user might try intellecast.com.
This page is provided by Jan Curtis, the premier Aurora photographer in Alaska, and probably the world. There are also many useful links.