In your opinion, what is the best library to crunch data AND build the web based reports in this context:
There are tons of Javascript data visualization libraries, but ideally I'm looking for something that integrates "off-the-shelf" with MongoDB, and that uses modern technologies (HTML5) vs. old (Flash).
If I don't find anything MongoDB specific, I might go with either Google Chart or D3.js, which looks awesome but maybe too "young".
Since you already specified D3.js, i heartily recommend Cube Time series visualization tool kit that built on
Its still in early development. But looks very promising. And one of the cool feature is it packed with websocket, this will be a interesting choice for real time data visualization for web. Have a look