Best Answer, bar none:
http://xsd2code.codeplex.com
I pulled my hair out for a full 8 hr work day, got nowhere with all the crappy solutions out there (XSD, CodeXS, XSDObjectGen, and others) and am not interested in paying $400 for the stupid commercial tools just to do this.
Then I came across this codeplex project... WOW! Where was this all my life?
And the best part... its actively being worked on, right NOW (2009), not an abaondoned crust pile from 2004 or some lame thing.
Enjoy!