ASCII Library for Creating "Pretty" Directory Trees?

Question

Is there some *nix tool or perl/php library that will let you easily create directory tree visualizations that look like the following?

www
|-- private
|    |-- app 
|    |    |-- php
|    |    |    |-- classes
|    |    |    +-- scripts
|    |    |-- settings
|    |    +-- sql
|    +-- lib
|         +-- ZendFramework-HEAD
+-- public
    |-- css
    |-- images
    +-- scripts

Answer 1

How about this example from Unix Tree / Linux Tree:

ls -R | grep ":$" | sed -e 's/:$//' -e 's/[^-][^\/]*\//--/g' -e 's/^/   /' -e 's/-/|/'