SwitchTower is an underappreciated product of the Rails community that is actually independent of Rails and could easily be used by J2EE, PHP, or any other type of application. SwitchTower automates application deployment across multiple servers atomically, with rollback capability!
Mike Clark has posted his elevator pitch for SwitchTower.
Can you deploy and roll back software releases this easily and consistently on your project? If not, I’d recommend you give the SwitchTower manual a read, especially if you aren’t building Rails applications. That’s right, even if you’ve never heard of Ruby or Rails you owe it to yourself to check out SwitchTower because its concepts aren’t specific to Ruby or Rails.