[rezaman]

Although the project is still pretty young, liquibase(http://www.liquibase.org/) is a solid opensource project for not only managing schema revisions, but inserting seed data as well as abstracting schema structure from DBMS.

Nathan also does a good job of applying submitted patches quickly.

[quicksilver03]

There are also other projects like:

DbDeploy http://dbdeploy.com/ DbMaintain http://www.dbmaintain.org/