It's not hard to generate polar plots in GeoGebra; but they are not native, so there is no direct support.
The technique is to define an angle, say θ, as a number/slider. In the input field type θ = pi, enter. Open the properties of θ and change starting value to 0, ending value to 2 pi, and animation to Increasing. Show the slider.
Type r = (some expression) in input field; enter.
Type P = (r cos(θ), r sin(θ)) in input field; enter.
Find Locus tool (4th tool in tool-bar, last item in list), click to select it, then click on P then on θ. A graph will appear of all possible locations of P for any value of the θ slider.
To see where the point is at any particular value of θ simply drag the slider. To watch it automatically go through all values, turn on animation of θ.
The grid can be changed to polar.
Here’s a GeoGebra file: http://www.wyzant.com/resources/files/268188/polar_technique_in_geogebra
For a quick look, here’s a GeoGebra generated animated gif: http://www.wyzant.com/resources/files/268189/polar_technique_in_geogebra_animated_gif