I've developed quite a few apps for iOS and am giving OSX apps a go. What would be the best approach to designing a UI like the split view on iPad apps? For a mac-based example, think of how the playlists work in iTunes. You select an option on the left, and a table view selects a different set of data based on what you selected.
Any ideas?
That sort of interface is known as a source list or source view. It's actually a special style applied to an outline view. Apple provides the SourceView sample code which illustrates the technique.