entity relation diagram from Models

Hi,
Do you know some tool (I hope open source) to create Entity Relation
diagram from rails Models ?
It would be nice !

thank you,
Alessandro

http://github.com/nelsonsilva/yUMLmeRails/tree/master

http://railroad.rubyforge.org/

http://stackoverflow.com/questions/481618/is-there-a-good-tool-to-generate-an-image-of-the-database-schema-used-in-a-rails