As I got deeper on Wordcloud of the Arizona et al. v. United States opinion, I ran across several resources on the tm package for text mining in R.
First, if you are in an R shell:
> library("tm")
> vignette("tm")
Produces an eight (8) page overview of the package.
Next stop should be An Introduction to Text Mining in R (R News volume 8/2, 2008, pages 19-22).
Demonstrations of stylometry using the Wizard of Oz book series and analysis of email archives either as RSS feeds or in mbox format.
If you are still curious, check out Text Mining Infrastructure in R, by Ingo Feinerer, Kurt Hornik and David Meyer. Journal of Statistical Software, March 2008, Volume 25, Issue 5.
Runs a little over fifty (50) pages.
The package is reported to be designed for extension and since this paper was published in 2008, I expect there are extensions not reflected in these resources.
Suggestions/pointers quite welcome!