I know this is a newbie question, but where in the rails tree should I place a my own helper classes? For example, I have a class called UserSchedule which loads data from different models in order to form a user's schedule. Should that go in the models directory? components?
I would put your UserSchedule class directly in the model directory as you suggested. Think of the model as containing all the 'business logic' of you're app, not just the ActiveRecord::Base derivatives.
If later, you end up wanting to share logic between applications, there are some helpful tips here, http://wiki.rubyonrails.org/rails/pages/TheBigPicture, on reusing your classes between applications. But for a single app, putting classes directly in model works fine.
“UserSchedule which loads data from different models in order to form a user’s schedule”
I put these kind of classes in the controller directory, because you are loading data from the db
If you just calculate a few vars, i would put it in the model directory, the good thing is that you can access it from helpers, views, controllers.