I just discovered, at Web 2.0 from Russia, that Google has a built in calculator! Go to Google and search for sqrt(-4). It even seems to give the correct answers, so far. If you really wanted to search for documents containing sqrt(-4) then search for +sqrt(-4). You can also do unit conversions and calculate currency exchange rates.

Here are instructions on correct syntax as well as another 3^2 examples. Now I just need to figure out how to best use this feature in the classroom.

Note: It doesn’t do as well with undefined terms such as 0/0 or 0^0.