Greg Militello: We use same aproach as Paul Rentschler with config files. As our production and testing environment passwords and keys are not visible to developers, but only for specific server admins. Each instance has it's own config.yml.local file which contains specific settings for each instance. There is also config.yml which has default settings which can be overwritten wtih config.yml.local.
Great article. I really enjoyed it even though i am already doing almost everything what is on the list. You can also add vagrant file with provisioning script to your source control. This way everyone on team have same environment. Not only that... everyone can start working on the projects in few minutes (or in hour if you are installing and setting up a lot of packages).
I am already working on virtual LAMP for virtualhost and vagrant. It has some neat features like automatically created virtualhosts with dns entries upon directory creation in /var/www... You can try it out here https://github.com/mhlavac/lamp-install-script, i hope to release first stable version with complete documentation in late May.