<p>Had anybody found a way to migrate MediaWiki pages over to WSS Wikis? We just put up Sharepoint 2007 and while it appears to meet our needs, it doesn't appear to be any tool provided by Microsoft to migrate MediaWiki pages over to WSS wikis.</p>

There is no such tool provided by Microsoft at this time.
There is one being developed though in the
SharePoint Community Kit
.
Wiki Import/Export Tool
The EWE team is at a very early stage of designing an import/export tool for the SharePoint wiki. The goal is for this tool to be able to import from other wiki products such as FlexWiki, MediaWiki, and TWiki, and Confluence and also from Word and OneNote as well as to export to Word via HTML (per page) and MHTML (entire wiki) formats.
For this CKS 2.0 pre-release, the EWE team is making available a fairly stable build of the FlexWiki Import Tool, for which the source code was graciously donated by Michael Cheng, a developer in the SharePoint product group. This is a one-off tool that will ultimately be converted to a plug-in for the Wiki Import/Export Tool, so if you’re currently using FlexWiki, please test the tool and provide feedback.