Geoboard from “The Math Learning Centre” is a great web app. This virtual Geoboard enables the user to stretch rubber bands around pegs to create lines or shapes. It can be used to explore angles, area, perimeter, and fractions.
There are three geoboards to choose from as pictured below.
You can set a grid and number it. You can fill shapes that you create with colour as pictured below.
You also have the ability to annotate your work as pictured below.
Geoboard is a well designed app that you’ll keep coming back to when the need arises. It is simple to use and something that students should intuitively be able to use.Geoboard Web App Geoboard – iPad iTunes link