Let me be clear - I'm not sure this is the best way to do this - but it worked and as it took me a while to Google up the answer and test it, I thought I'd share.
Ok - so imagine an entity that has a many-to-many relationship. A good example is a blog entry with many categories. Any one blog entry may have multiple categories assigned to it. How would you write a query to return all blog entries in a specific category? Here is how I did it (and I apologize for not linking to the post - I forget exactly what I saw this):
<cfset r = ormExecuteQuery("from blogentry as be left join be.categories as cat where cat.id=4")>
Obviously the 4 there is hard coded and would be replaced with a bound parameter.