Module to allow multiple paths for a single node? Is there a module that would allow me to define multiple paths for a single node? (Not just one node; I need to do this for multiples.) For example, I need to be able to access http://www.example.com/node/153 via both http://www.example.com/tracks/big-picture and http://www.example.com/big-picture.

I need to be able to define at least one of the paths manually, i.e. not using a pattern.
You can already do this using core's Path module in Drupal 6. If memory serves, it should be in admin/build/path/add. Simply create two aliases that both point to node/153. 

I should caution, however, that this may raise red flags with search engines. They typically frown on duplicate content, and your SERP rankings will likely suffer as a result.