What are my options for MVC, GUI + Interactive Visualization in App Engine (python)?
Does it have to be in python? The GAE has wonderful support for GWT. The GWT eclipse plugin can compile and deploy directly to the GAE with no further modification. The best solution that meets all three of your requirements will be to use GWT + GAE/J.
If you're mainly looking for a charting/graphing solution, there are some good solutions based on Flash *gasp* that are pretty easy to use, such as AnyChart.
As a side note, If you're designing any UI, knowing and understanding the MVC pattern is essential. Most other UI design patterns are a derivative of MVC, so you'll probably be learning MVC regardless of what framework you choose.
Good luck
-tjw
I'm creating an app that allows users to query, manipulate, and explore a very large graph.
What's the 'best' way to create a gui + visualization for my project?
By best I mean the following:
1. conforms to web standards, no flavor of the month solution
2. allows creative flexibility
3. intuitive, won't require weeks to learn and months to master  
Should I start diving into Django and learning how its MVC works?  Everything I've read pisses on Django, but seems like the most used option for GAE.  
I'm sorry if this isn't coherent. These technologies are out of my comfort zone, so I have trouble searching for solutions and phrasing my questions.