[Updated 7/20/09: The module is now live on drupal.org, so I have removed the tarball from here.]
Envts (Environments) module
This module was created to fill the need for *two-dimensional* environment/host management.
* What's an environment? An environment is a development or server location where a full Drupal build (possibly including multiple hosts) is set up. In our work, we tend to have
1) a primary 'dev' environment (site.dev.ourwork.com),
2) local environments for each developer (site.dev.local),
3) a staging environment (staging.site.com),
4) a live site (www.site.com), etc.
But each of these can have multiple hosts, making the number of actual hosts to track and toggle grow exponentially. The domain_access module does a good job of tracking hosts, but in only one environment. The Envts module simplifies the process of managing these sites.