Here’s an interesting post that explains to plugin authors how to make full use of their readme.txt file. The purpose of the readme file is quite clear, it helps the WordPress plugin repository to apply the right captions and categorisation to you plugin. This is more important than ever, now that they have improved their search engine.  The readme file contains the following sections:

• Plugin Name
• Description
• Installation
• Frequently Asked Questions
• Screenshots
• Other sections

And should be populated well for the site to help your plugin get found. The post also talks how you can use comments on the plugin to supplement this information. It’s worth using this functionality well, because besides making custom rubber stamps and stamping every plugin as it goes out of the door (which would only work if you’re mailing CDs), I don’t know of a better way of getting more downloads of your plugin.