It's not often that this blog tries to sell you things, but this one might really be worth it. MacRuby is an emerging Ruby implementation that can be extremely useful to OSX Ruby coders. It allows you to easily interface with many native OSX APIs, including Cocoa and Grand Central Dispatch. But information about MacRuby can be hard to find. Well Renzo Borgatti has created a 48 minute long screencast explaining many of these features, organized into 14 chapters. The screencast is available now for $8.99, an excellent price.