Hi there! My name is Joel K. Pettersson, and I've sometimes made small contributions to various MediaWiki extensions. I know Swedish and English.
I maintain the following extensions:
My main interests in the world of MediaWiki software are Semantic MediaWiki (and similar extensions), scripting support (where I find PhpTags the most interesting option so far), and generally what can be done with more advanced data storage and querying features.
I think the most commonly used approach of providing extension features only through parser functions limits the flexibility of how those features can be used and combined. Scripting provides a more general and powerful way of handling data, and can potentially be used to pass it between extensions. It also has potential for building upon the functionality of types of extensions in a more generic way.
If you wish to email me, I use Gmail and I'm "joelkpettersson".