Data Visualization Aggregator
visual.ly followed by visualizing.org. (preferred visual.ly since it felt a little more vibrant than visualizing.org)
Visual.ly is website / collection of info graphics and data visualizations and is updated frequently. It’s like dribble but for info graphics.
In this TED talk, Jonathon Harris maps certain emotions gathered from data all around the world (on the internet) and looks at in relation to other variables like weather / day / gender etc.
Artist / Designer
From the tools I researched on, Processing seemed to be the most versatile and powerful. It allows you to take the visualization to almost any direction possible.
Data Collection Tool
Due to its spreadsheet format, I think Excel is one of the best tools to view and re-arrange data.
I did not find a specific forum for Data Visualization, but there are many data visualization threads on various websites. These threads are usually either on websites that host tools for data visualization or websites that share data visualizations.
As a whole, I think data.gov is a very useful data source because of its size. This followed by data from social networks, especially when coupled can be very useful.
As much as it talks about it ethic, this article is also a guide to visualizing information in general. The cherry on top is the oath at the end of the article.