Just a tip that worked for me. I followed the instructions here:
http://discover-doug.com/2007/01/25/installing-tinymce-with-drupal/

Basically it is a two part process, installing the TinyMCE libraries first, then
the module for Drupal. The location for installing the files is different compared
to Drupal 4.x

TinyMCE still wasn't showing up until I switched to the default theme.

To fix the theme I was using (andreas09), I added this line to head tags in page.tpl.php:
print $scripts

Voila! All good :-)