For the past few months I have subscribed to the Taxacom email list. I have tried a number of listservs over the years and I have usually regretted it fairly quickly. Most listservs seem to be plagued by off topic posts and flames that take over and waist everyones time. However, I have been pleasantly surprised with Taxacom.
While there are certainly people who have an ax to grind on particular topics, the discourse is as a whole civil and intelligent. As a student, this has been a great learning tool for me. I have been able to sit on the sideline and observe as professors from great universities and directors of important collections from around the world debate issues such as: the definition of a species, phylocode, open source publishing, and many other topics.
If you would like to search the archives of Taxacom or join the mailing list just go to their web page.