Miller columns

Da Wikipedia http://en.wikipedia.org/wiki/Miller_Columns:

Miller columns are a browsing/visualization technique that can be applied to tree structures. The columns allow multiple levels of the hierarchy to be open at once, and provide a visual representation of the current location. It is closely related to techniques used earlier in the Smalltalk browser, but was independently invented by Mark S. Miller in 1980 at Yale University^{[citation needed]}. The technique was then used at Project Xanadu, Datapoint, and NeXT.
While at Datapoint, Miller generalized the technique to browse directed graphs with labeled nodes and directed graphs with labeled nodes and arcs^{[citation needed]}. In all cases, the technique is appropriate only for structures with high degree (large fanout). For low-degree structures, outline editors or graph viewers are more effective.

A Miller Column browser as implemented by GNUstep. It incorporates a Shelf.

Finder Basics from Apple