Good tool to visualize data?
araneae: Flot is super cool but probably a bit off-topic for your needs http://code.google.com/p/flot/Every time I try to use R I just say "fuck it" and use Matlab.  Matlab is pretty flexible w.r.t. manipulating data and there's a lot of tools to deal specifically with time series analysis http://www.mathworks.com/access/helpdesk/help/techdoc/data_a...The open source version of Matlab is Octave but they aren't really comparable.  But if you're dead set on open source, that's what I'd recommend.If you want the flexibility of Matlab and the prettiness and manipulation ability of flot, Mathematica produces some pretty elegant figures, but I hate the notebook interface.  Yes, I know, you can use a command line interface with it but the UI for Matlab is actually useful and awesome (like being able to see the contents of all the objects you create.)