Scribo is a LaTeX editor which focuses on navigation in large documents with multiple files. Scribo brings a live outline of your document which displays all \part, \chapter, \section etc. It even displays file includes (both \input, \include and \bibliography) which results in rapid access to the entire document. Try it out for your self and see how much difference it makes to be able to access the entire document without leaving the writing environment...
Mac OS X 10.6 Intel