Peter's R Programming Pages: "R is a language and environment for statistical computing and graphics, available for free from The R Project. It is very similar to the S language and its commercial derivative, S-PLUS.
Have a look at this R Graph Gallery for an idea of the sort of images R can create.
If you are working with microarray data then you should really look at the Bioconductor package, a set of freely available biologically useful statistical tools."
