Because of all the hype and because I was not very much convinced with Perl or Python, I started to gather information about Ruby. Obviously I finally reached the Ruby Mail Lists (a great source of information about Ruby). But something catched my eye and stunned me: the beauty and confort of the web interface they had to read the Maillists:

The beautiful web interface of the Ruby Mail List
I was not able to find out what is the software they use to handle it. I am quite sure it is made on Ruby, but probably is custom made. It will be great if it was available, because it seems a perfect approach for a good webmail tool. Really impressive... simple but yet powerful.