Funny that you should ask this today. I was just about to look around the monastery for the same.
I'm just now finalizing a system to automatically determine if general news articles in a large newsfeed is 'bad news or good news'. i.e. to mark negative events, if its negative stock market reports, a local sports team losing, negative criticism, crime etc.
Perl has been excellent for implementing such a system and I find the tools at CPAN invaluable, but as I only work with Scandinavian languages a lot of the modules are not available to me as they are a too specific to English. I would guess that the stemmers are a basic tool for everyone doing computational linguistics, though, and they are available for all the languages I need them for.
Mats Stafseng Einarsen