A Better Calculator is a new, free, online graphing calculator from Demos (who also offers a service to create online interactive media). There is nothing to download as it runs online. It is easy to use, full color, full functioned. You can share your work online or even share it with others (like your students) or students can share it with their teacher.
The screen is nicely laid out with the functions and expressions on the left and the graph on the right. There is help available and even some examples to look at.
It is also now built with HTML5 so it works on all devices, including the iPad.
This could easily replace all those expensive graphing calculators that students have. I was able to access and use this on my smartphone browser also.
Free Online Scientific Calculators
Desmos - create media rich educational content online