Games for your brain and look at the sky

Fun 4 The Brain has games and activities for math, science, and English.
Academic Skills Builders has more online games for learning basic math, language arts, vocabulary, and thinking skills. This site even has links to math standards for the different states.
And, here is what the blog Recess Duty has to say about Mind 360: "It’s educational, interactive, free, and addictive. " (and it isn't just for kids)

Leaving the world of games...
WorldWide Telescope is a rich visualization environment that functions as a virtual telescope, bringing together imagery from the best ground- and space-based telescopes to enable seamless exploration of the universe.
Choose from a growing number of guided tours of the sky by astronomers and educators from some of the most famous observatories and planetariums in the country. You can pause a tour at any time and explore on your own. Or you can stop and research a deep sky object with the multiple information sources available. When you’re ready, rejoin the tour where you left off.
Turn your computer into a “virtual telescope” with the WorldWide Telescope. You can download an application for Windows, or use the web-based version for Windows or Mac.