Green Fluorescent Protein (GFP) is a great site for science teachers. It talks about the discovery and uses of fluorescent proteins in science. There are some great applications as well as some controversial ones, so there are plenty of opportunities for classroom discussions.
There are some really impressive pictures, descriptions of the uses of GRP, links, classroom ideas and more. The college professor who runs the site is very approachable and will get back to emails and will help you use the material in your classroom.
It's an interesting topic and the pictures alone can get your students' attention.