Tim Starling has set up a portal at www.wikiversity.org. The way it works is simple. There are two pages on meta that define the contents:
http://meta.wikimedia.org/wiki/Www.wikiversity.org_portal http://meta.wikimedia.org/wiki/Www.wikiversity.org_template
The content of the portal is wikitext which is inserted into the content of the template, which is HTML (the template therefore needs to be protected, as it can contain JavaScript and the like). You can see an elaborate layout at http://www.wikipedia.org/ , which is made of:
http://meta.wikimedia.org/wiki/Www.wikipedia.org_template http://meta.wikimedia.org/wiki/Www.wikipedia.org_portal
I would suggest that a call for participation is added to the en.wikiversity.org sitenotice (MediaWiki:Sitenotice) to make a nice portal.
Because MediaWiki renders the HTML in a very ugly fashion, those who want to work on the design should probably do so in an HTML editor and then ask a Meta sysop like myself to copy it into the template page.