On occasion I encounter this problem but I never remember how I fix it the time before... which is annoying for myself.
I have the following find: @conversations = Message.find(:all, :select => "DISTINCT from_user_id, created_at", :conditions => ["to_user_id = ?", session[:user_id]])
I want distinct from_user_id but at the same time I want to have other fields removed like created_at. If I return more then from _user_id I am not getting distinct from_user_ids...
What is the rails way of solving my problem? 
Thanks eveyone for helping me out!