Where should I put the technical documentation ? And the functional ? In which format (RST, HTML, ...) ?
Since version 7.0, the official technical documentation for each module is in its doc/ directory in the RST format. For instance, the web and mail addons have such a doc/ directory. The doc/ directory for the framework is at the root of its source tree (i.e. alongside of the openerp/ directory).
To write new documentation for a module that do not have such a doc/ directory, the best thing to do is to mimic what is done in web and mail.
The official documentation is built automatically on doc.openerp.com. (There is no specific documentation for 7.0. Instead doc.openerp.com/trunk applies.)
For unofficial modules the same convention can be used but a service such as readthedocs.org would be used to publish it automatically.
Hi Anto! I leave it up to you to decide whether this'll be 'the best' way to write documentation for your custom-built OpenERP module and give it some visibility... However do know that we recently launched our website 'OERPtuts', where we'd like to post the exact same information as you described in your question.
Please feel free to contact us through our contact form at www.oerptuts.com/contact/ if you should be interested to receive some brand awareness for your custom-built OpenERP module. At the time of writing OERPtuts is still brand new, however you'll already find some extra information in our first launch post at www.oerptuts.com/articles/news/launch-time/. At our website, you can also subscribe to the OERPtuts Newsletter to receive automatic updates of future posts...