WolframAlpha has some pretty awesome Widgets in Beta testing right now. In fact you can easily create your own widgets.
Some of these are great for higher level maths, but I think they could be quite useful in the lower grades as well, particularly for investigating patterns. They’re also not just for Math, but could be useful for Biology, Chemistry, Business and Finance, Humanities, and are really open to any good query searches.
Finding the widgets is quite simple. Head over to WolframAlpha.com Widget Gallery and then browse for an appropriate WIDGET.
Once you’ve located the widget that you want you can select the EMBED button on the right and it will give you the source code to EMBED the widget into your page!
If you want to create your own widget then at the top of the page instead of browsing you can select BUILD A NEW WIDGET.
You can even insert a Wolfram Alpha search right into your page by going to: http://www.wolframalpha.com/addtoyoursite.html