ScienceFix is a great resource for science teachers, or anyone interested in science. It is targeted towards middle school, but can be used at different levels. It is run by a science teacher.
It has science lessons, links, video demonstrations and web projects on science. There are a lot of great resources here. The video demonstrations alone are great to use as an engagement tool, or as part of a lesson. You can browse or search for lessons and resources. The site also encourages comments and discussions about the resources.
Check it out: http://www.sciencefix.com/