This is one of my first attempts at making a Cocoa app. I wanted to create a log viewer for Rails development logs. Down the line, it'd support features like sharing problems you see in your log, syntax highlighing, and code folding. For the time being, it's a rough prototype that can read Rails 2.x logs files.
The main log viewing window is a webkit view that uses the Javascript bridge to communicate with the Cocoa app. When a new log file is opened, a new Log document is created and watches for changes in the log file. Changes are pushed out and processed by Javascript to form log entries.