Finally, I've been waiting eagerly for this. OpenMCL now has a Cocoa bridge. This allows you to use Objective-C frameworks from Common Lisp. The advantage: virtually the entire OS X API (at least the part that came new with OS X) is now potentially available for Common Lisp. Integration with other Objective-C programs is also much easier. And there's finally a chance to develop a usable GUI via OpenMCL. There's also already documentation on Cocoa programming under OpenMCL. Here's the original article.