This week's book giveaway is in the Other Languages forum. We're giving away four copies of Functional Reactive Programming and have Stephen Blackheath and Anthony Jones on-line! See this thread for details.
It allows you to generate DDL from mapped classes. You can use this is you don't want the overhead of maintaining your own database scripts, however you need to be aware that the data model Hibernate generates this way and the data model you might want may be different.