Good tool to visualize data?
jjguy: The suggestions below are solid:  R 
  Python + matplotlib

I've used and been impressed by both.  Starlight and Palantir may fit your needs, but those tend closer to enterprise applications -- I get the sense you're searching for something lighter.Some more suggestions:DAVIX [D]  A live CD distribution containing lots of visualization tools, from capture to parsing to presentation.SecViz and their "graph exchange" [0] -- lots of pictures of various datasets, usually with details of how it was produced.Personally, I found most packages too restrictive and fell back on Processing: http://processing.org  A project out of the MIT Media Lab, it's a generic graphics framework you can (among other things) produce 2D time series graphs in. It's still tedious, but tedium is traded for control.Some of my projects in Processing:http://jjguy.com/som/ - Self Organizing Mapshttp://jjguy.com/life/ - Conway's Game of LifeI don't have a great time series write-up posted, but I've been working with Robert May's population model recently. [1]  You can find the source at [2] and example output image at [3].[D] http://secviz.org/content/the-davix-live-cd[0] http://secviz.org/category/image-galleries/graph-exchange[1] http://en.wikipedia.org/wiki/Logistic_function#In_ecology:_m...[2] http://jjguy.com/populationModel.pde[3] http://jjguy.com/normal.png