How could you possibly improve on perfection!  Well, if I had to mention something it would be a link to the finished/large JPG for each tutorial.  You already have this option for some of your tutorials, and it's so nice to be able to see them/refer to them as you go along.

As for posting them on Renderosity, I don't see any reason to double up as long as you keep posting them at Geek at Play.