The problem with the data modeling tools is that the common ones -- ERwin, PowerDesigner, ER/Studio -- are all expensive ($3,000 or so) and surprisingly mediocre. I spend a lot of time in ERwin (and I used to teach PowerDesigner as a certified Sybase instructor), and it's just amazing how many bugs, unintended "features", and missing features are in them. (Not a one of them can do a decent job doing an automatic layout of a reverse-engineered database, even though reverse-engineering was one of the top uses of the tool in every PowerDesigner class I taught.) I suppose we could do one of the "web publish" deals, but I don't know if that's really helpful.
