I like this macro example from http://common-lisp.net/cgi-bin/viewcvs.cgi/cl-selenium/?root=cl-selenium It's a Common Lisp binding to Selenium (a web browser test framework), but instead of mapping every method, it reads Selenium's own API definition XML document at compile time and generates the mapping code using macros. You can see the generated API here: common-lisp.net/project/cl-selenium/api/selenium-package/index.html
This is essentially driving macros with external data, which happens to be an XML document in this case, but could have been as complex is reading from a database or network. This is the power of having the entire Lisp environment available to you at compile time.
