There are several good sources online for how to build a solar still. Videos, articles. I came across this text, and was really impressed:
http://www.builditsolar.com/Projects/Cooking/SOLRSTIL.HTM
I'm building a roughly 3x4 ft solar distiller using a salvaged plate of glass. I am making the body from ferrocement (dyed black). The water channel will be concrete as well. I will use PEX tubing covered in something or another to prevent UV exposure/damage.
Fun stuff.