In standard php or source code based projects we easily keep all of the code in SVN and each developer can checkout their own copy and collaborate on the same code.
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Taking Drupal settings from the database into code had been moving forward in leaps and bounds. Two modules that really help in this realm are:
Features - Allows you to gather together entities such as content types, taxonomy, views, even feeds. We are using this very successfully and it's made it possible to share these changes between developers.
Strongarm - Allows for the storage and export of the variable using the above module. I've done some testing with this module but we are not using it, simple because we really didn't need the functionality.
These solve the biggest issues with keeping the site setup in the database. They are not perfect however. . . we've found modules that were not supported or supported incorrectly.