Where to "spawn" (background tasks in a rails app)

My rails app is using the spawn plugin to run some background tasks.

I'm wondering what is the most appropriate place to put a call to
startup those tasks.

I'm thinking probably somewhere in boot.rb, though I'm not sure which
method, and maybe it is inappropriate to put my own stuff in there. I
looked around and did not find anyplace that seemed pre-ordained for
startup tasks. (in the same way that we have pre-ordained directories
for the MVC components etc.)

Can somebody who has set this up before give me a suggestion to save me
from a bunch of trial and error?

thanks,
jp