There are a number of web-based applications and tools that have relevance to science teachers. These tools can be used directly in classroom teaching, as a means to communicate with students and other colleagues, or to organize and share learning resources.
Here are a few that I have used my or experimented with in my own teaching. I am continually looking at ways to effectively implement technology into my own teaching and I would love for you to share your experiences and resources with me (firstname.lastname@example.org)
Bubbl.us is a tool for making concept maps
Dropbox allows you to access files from anywhere
MediaFire unlimited online file sharing
Poll Everywhere lets you perform informal assessment via text messaging
Prezi allows you to search and create presentations for your classroom
Wordle is a tool for generating word clouds from text that you provide