Microsoft Visio Enterprise - we used it because we had it
Computer Associates - ErWin
Embarcadero Technologies - ER Studio

There were a couple of other vendors when we were shopping for tools like this. It turned out that we already owned Visio Enterprise, so the boss made the decision for us.

ErWin and ER Studio both have downloadable evals, I think...

There was another one we considered looking at, but the name escapes me because I had a whole 3 hours of sleep last night.

Glen Austin