Come hack on your personal visualization projects. There's no set discussion topics-- just people with laptops.
If you're just getting started with d3.js you're welcome to come by to work through tutorials with other beginners. Experienced users will be around if you get stuck. It's recommended you at least work through A Bar Chart, Part 1 so you can dig into more advanced topics at the meetup:
The wiki has a comprehensive list of resources:
There's a Python class in the space beginning at 7:00. Python is a great language for cleaning data, transforming into JSON, and hooking into databases. If those are things you need to do for your project, find details on PyClass here:
If you're an experienced d3 user, consider using the time to create a d3.js chart class: