I spoke at Code Generation 2010 at Cambridge in the UK on my experiences implementing code generation in various parts of an existing shop's development process.

One of the low-hanging fruits in that regard is selecting existing and under-utilized models and making the most of them.

I found that SQL schemas were a great way to model a business domain even if you need to migrate to another database ... since you have so many tools (including free cross-platform visual ones, like MySQL Workbench) at your disposal, validation, decent type selection, options for more complex validations using triggers, everyone knows it (unlike UML), etc.

Another great 'model' that people are usually sitting on top of, also ripe for code generation, is the software dependency databases in many distributions.

Another is your RCS/VCS system.

Another is - and here comes the kicker - the filesystem, which with modern tools (inotify, etc.) can give an impressive amount of RCS/VCS style functionality (COW, event notifications, etc.) at kernel level.

What was that quote again? "Unix is simple, it just takes a genius to understand its simplicity". They weren't lying.