What do I need to write glsl shaders?

What do I need to create glsl shaders? Is there a special software that I need to write and compile it?

Here’s a video tutorial:

Nothing special is needed. As Goran pointed out, you can do them in Blender and you can also do them directly in this website if you want http://glsl.heroku.com/.

Very helpful! Thank you!

or, you can learn cg/hlsl first. There’s much more tutorial on that topic. Once you learn the basic concept, you can switch to glsl. You can use rendermonkey for testing glsl/hlsl shader.