As quantitative analysis stays very important, but becomes more and more popular and easy to do, I would like to give a brief overview about tools I found that can help you to do this. The tools have different strength and weaknesses and also different pricing and license models. I hope you find it helpful. If you have additional suggestions, please let me know.

Tableau Software

Spotfire

Time Searcher 2

Panopticon Explorer

Swivel: A detailed review is given on Infosthetics

Many Eyes: A detailed review is given on Infosthetics

Overview about different topics around social visualization

Have fun reading and trying. The list and article will be expanded if I find some more interesting tools.