PathSnagger (Previously CopyPath)
Requires Mac OS X 10.1.

PathSnagger adds a Contextual Menu Item option to the Contextual Menu in the Finder. Control-click a document, application, folder, mounted volume, zip disk, anything, and easily copy the full path to that item directly to your clipboard!

Screen Shot
Reviews

Currently enjoying a rating of 5.0 at VersionTracker.

Chez Mark: "Not glamorous, but get high marks due to its inherent usefulness, simple operation, and freeware goodness." 4.5 stars

from TuCows.

from MacUpdate

PathSnagger is freeware, but donations are very much appreciated!