@bsugar here...I should add...despite being very aesthetically pleasing, this graph was created to help answer the questions "How many posts are tool related?" and "Which tools are being worked upon/employed where?". There are two issues with answering these seemingly simple questions: 1) since there aren't any standard tags in a folksonomy, it's not gauranteed that picking up all folks with the tag "spectrometry" (for example) will be inclusive of all posts that are actually about that. 2) we don't know of all projects happening in all geographical areas. 3) We have over 6000 unique tags on the site. So the idea here was to create a graph of tag co-occurrences and then analyze them as though there were communities of tags. Take a look at the bright orange cluster on the right which has a lot to do with air quality, and also contains the tag with the location of Wisconsin.

This looks like a really good result that answers a lot of your original questions. I guess most people don't tag their notes with a location, so there is only a partial answer to the location question.