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 diagrams.

What is the best way to document a rails project?

Best, M