I am under the impression that you are interested in statistical graphs?
In that case you should consider trying 'R' at http://www.r-project.org/
This is a cool statistical package, however do not expect much graphic interface involved. But it is free, and with some work the results are really good looking.
A lot of documentation is available on site.
You could install it on your machine and 'play' the graphic demo (type"demo(graphics)").
You could also check out Octave and Kmatplot (a matlab like soft), and Xfig could sometimes be helpfull too.
Hope this helps,