Riding the Rails with Locomotive
After having some trouble compiling lighttpd on my powerbook, and not really feeling like updating my version of automake, I decided to try Locomotive which includes lighttpd, mysql and postgresql bindings, SQLite, and bundles for Rails 0.14.1 and Rails 0.14.2. Installation was drag-n-drop per all good Mac software, it doesn't interfere with your current Rails installation, and thus far the operation has been seamless for me.
I really like the way they are integrating it with other Rails/Mac-centric tools like TextMate (you can open your project via a menu) and preferences for the Mac OS X terminal or iTerm. You can also preview apps in the default browser (no preferences for different browsers).
The interface is simple, clear, and unpretentious. Just like RoR!