Publishing stable APIs would be terrific, especially if they returned JSONP so that JavaScript could access Lernu.net web services directly instead of using an intermediate web server.

For example, I create a site at:

Mobile EO

This GWT based web application uses a PHP server to in turn access Lernu.net for 'Word of the Day', 'Word Translation' and 'Word Definitions'. The Lernu API is simple and the PHP does very little other than just acting as intermediary. However, it is a two step process which add a few milliseconds to the fetching.

The source code is available on SourceForge as 'Mobile Esperanto' and as a demo project (Under development) on GitHub using SmartGWT Mobile, 'SmartGWT-Mobile'.