If you want to test shaders or learn about them here is my idea.
I think you should try the trial version which is PRO by the way and it is available on the download page
http://server.conitec.net/down/gstudio_setup707.exe
and when you see how much the shader is beautiful you may start save some money to buy it in future.
No ... if that was your answer, I will suggest you to go to nVidia website and download FX Composer 2.0.3 which is dedicated for Shader creation and there is a shader library that is available online, or you can download the nVidia SDK 9.5 but to use the shaders that comes with it you should install FX Composer 1.8
NOTE: there is no problem installing multiple instance of FX Composer in the same machine.....

FX Composer available at this link:
http://developer.nvidia.com/object/fx_composer_home.html

I hope this help ....
Mysterious