Rails - Jan 2006 - auto_complete with 2 related tables

I''m looking for a wiki / example of how to use auto_complete with 2
different tables so you can use the values in the column of one table to
provide a value for a column in a related table.

This concept apparently comes after my Agile book and is important to me
and I would think should be important to others and I simply cannot make
it work. 

Anyone have a reference they can point me to?

If not with auto_complete...how about using collection_select?

Craig