Hi there,
Have you seen this plugin by Ilya Lebedev:
http://wiki.splitbrain.org/plugin:indexmenu2
- Shows a tree menu for a namespace
You'll need to put it into the sidebar.txt file used by some templates
- based on the sidebar function by Christopher Smith
(I use 'battlehorse' - by Riccardo Govoni - which I highly recommend)
Cheers!