For ad hoc Rails tasks we have a few implementation alternatives, chief among which would seem to be:
script/runner some_useful_thing
One thing I've done is just write normal ruby scripts and put them in the script/maintenance
directory.
All you need to do to load rails and get access to all your models, etc, is put require '../../config/environment.rb'
at the top of your file, then you're away.
For one off commands script/runner can be fine. For anything repeated, a rake task is easier in the long-run, and has a summary if you forget what it does.