I've seen that gallery, but it's more a showcase of external projects than a bunch of feature examples.
The NodeBox gallery shows a lot of cool projects (something that Graphviz and matplotlib only hint at), but it's not much use for a new user who wants to look at pretty pictures, and then tinker with the code.
If you want to find out how to draw a graph in NodeBox, you click on the "graph" gallery. Then you click on the "graph" wikilink. Then you scroll through the graph tutorial until you find some code that you can run. You still can't re-create the gallery picture, but you can do something similar, I guess.
In graphviz and matplotlib, you go from the gallery image to the code that created it in one click. It's much easier to discover their features.
Like I said though, NodeBox looks very cool. The images are slick, it looks very powerful, and the community looks very smart.
Separating them (or just tagging the ones that can be pasted into the code window) would be nice.
The real issue is that everything useful (the tutorial, reference, and library) is indexed by command name. The graphviz and matplotlib galleries index the commands by pictures. That's a lot more discoverable and visual.
