"If you need to perform data analysis, provide graphics for your users in your webapp, or produce high quality plots I encourage you to investigate the combination of ruby, GSL and GNUPlot." Looks good. I should probably give this a poke some time; could come in handy.

"This has to be the most quick-and-dirty data visualizer out there: I wrote an ascii art plotter script that takes a column of numbers on stdin and throws out a plot on your console." Oh, that's going to come in handy.