Feedly.com a simple web aggregator that will pull in blogs that you choose to follow, allowing you to read them all in one place. If you use Wordpress, or even if you don't, it offers both an aggregator and a top notch service for creating your own blog.
Dippity An online timeline creator that allows pictures, dates, and information. It does require registration, but is easy to use and is web-based.
Gapminder A resource for using graphs; especially helpful in a high school Geography classroom.
Meograph A more advanced version similar to Prezi (demonstration). Allows you to import pictures, video, place comments, and set it to music. The program is web-based, but allows very creative montages and easy sharing as the finished product is hosted by the site. It does require registration, but is free.
Movie Reviews The website, Kids in Mind, reviews hundreds of movies for profanity, nudity, and violence. When these things show up, they give you a detailed explanation of what appears in the film, so that you can be better prepared when you forgot that one part of the film that had so much going for it.