Dynamically Generating Pretty Web Based Charts/Graphs
I would recommend the awesome d3.js package, you can do just about anything with it and it produces beautiful interactive charts.
I'm using Python to work on a web app that has a data visualization element. Basically, it will gather data about a user's music catalog and allow them to visualize it and take actions based on what the data tells them. I'll pretty much exclusively need bar graphs to achieve the visualization I want. Given the dynamic nature of the app, the package needs to support creating charts on the fly -- essentially responding to a user's commands and their data to quickly render a new chart. 
The problem is, some of the more lightweight packages like PyCha create charts that aren't visually appealing or suitable for a consumer based web app. I've looked into Fusion Charts, but that seems a bit heavy weight for my purposes, and it uses Flash, which I'd like to avoid. 
Is there a nice middle ground somewhere that allows me to create reasonably pretty charts based on user input but doesn't bog down my server with Flash baggage and an enterprise level amount of features?