How can I detect if my code is running in the console in Rails 3?

You could try this perhaps

if defined?(Rails::Console)
  # in Rails Console
else
  # Not in Rails Console
end

Many years later there is a better method to do this registering blocks to run for the console (using the railtie interface).

So in the initializer you can write:

Rails.application.console do
  # your code here
end

The good think about this is that it also works for runner and it should also work with spring (but I didn't test that).