What a coincidence!  This is precisely the topic of the talk I'm presenting at the ATEG conference this Friday, where I am off to as soon as I finish checking my email.  Although I have not yet done so, I was hoping to construct a website that reports on the studies I've been doing of the various software packages we have in our Writing Center, linking off of the Bowie State Unversity Writing Center website
at:
http://www.bowiestate.edu/departments/academic/english/WritingCenter/writingcenter.htm
The link is not yet on there, and I am also trying to determine if others have already constructed such a site.  PLEASE let me know what you find.  Thanks.
By the way, we have been using LearningPlus, Writing Tutor IV, Expressways, Grammar Workouts, and the various OWLs onthe Internet.