Improve the Documentation
Improving the documentation would be great. To be quite honest as a new developer trying to add on to Mange blog is pretty hard because of the lack of documentation.
There needs to be documentation outlining all the data that is stored, the order of operations of each page. What each page associates to, A better example of how to write an addon, better example of how to write a theme, ect.
A documentation wiki is now online, and all are free to register an account and contribute to the docs: http://wiki.mangoblog.org
If you have any specific questions, please post them as comments to the FAQ page, and we will try to address them on the wiki somewhere: http://wiki.mangoblog.org/wiki/FAQs.cfm
Expanded documentation for Mango would be very helpful, both from a developer point of view and from an end-user point of view. I would place the priority on the developer documentation over end-user, but both are important resources.