In Windows, I am looking at generating professional graphs using any mainstream programming language (C#, VB.Net, Java, PERL, etc). The best free looking graphs I have found so far is Microsoft Chart Controls for .NET. What other graph controls/modules do you suggest?
Note: Added free to the requirements.
jFreeChart is [one of] the best solution[s] out there for Java. I totally recommend it.
There are dozens and dozens of commercial charting components out there. Personally, I like the DevExpress tools.
XtraCharts is really good, well documented and relatively affordable.
GLE is a scripting language designed for generating professional quality graphs and diagrams for publication. It uses LaTeX for typesetting, so including equations in your graphs is a snap and they look great. Christopher Bishop used GLE for all the diagrams in his textbook, "Pattern Recognition and Machine Learning," and let me tell you, they looked great. Open-source to boot!
First you write the GLE script and tell it to accept a text file as the graph input data. Then, you can generate the data set in whatever language you want, export as a text file, and call the GLE script to generate the graph.
More info from the website:
GLE (Graphics Layout Engine) is a graphics scripting language designed for creating publication quality graphs, plots, diagrams, figures and slides. GLE supports various graph types (function plots, histograms, bar graphs, scatter plots, contour lines, color maps, surface plots, ...) ... GLE's output formats include EPS, PS, PDF, JPEG, and PNG.