You should also check out Dezign from Datanamic :-
http://www.datanamic.com/index.html
It is very affordable (about $200) compared to products like ERWin, and has a separate add-on for MySQL, which keeps the overall price down.
There is a free download evluation version, which never ran out last time I checked.
You will find it listed, along with many other, on this page on the Database Answers web site :-
http://www.databaseanswers.com/modelling_tools.htm
You will also get an idea of what the Data Models look like from the dozens that have been created using Dezign on this page :-
http://www.databaseanswers.com/data_models/index.htm
Hope this helps.
B.Dimple
Junior DBA