What is best way to document RoR app for 3rd party devs?

Hi all,

My role at my job is evolving away from rails dev and into a completely
different field and I have been asked to document my rails app so that
others can maintain/enhance it in the future. What are the best ways to
document a rails project so that others in the community could pick up
my app quickly and easily?

A brief description of my app: I have been developing and maintaining an
internal rails app for my firm (a small twenty person finance company
where I am the only programmer) for about three years now. This app
generates reporting and support data for a wide variety of functions for
various people across the firm. The reports are generated by about
twenty different rake tasks that are set up via cron jobs to run
throughout the day.

I was planning on just rdoc’ing everything as well as possible, and then
writing a manual in Word to accompany it, maybe with pictures and

What is the best way to document a rails project?