This is to announce a new extension of mine, called "Replace Text". This extension creates a new special page, "Special:ReplaceText", available only to administrators of a wiki, that provides a simple form to do a global string search-and-replace on the contents of all non-Talk pages of a wiki.
There's nothing semantic per se about the extension, but it was developed in large part for usage with Semantic MediaWiki. Since SMW's page properties don't follow redirects, the only way to handle renaming a page that's the object of semantic properties is to manually change each of the pages that link to it; if there are dozens or hundreds of such pages, this can become a difficult task. It's come up as an issue on some of the wikis that I've handled, and this extension has helped; I assume it could help others as well. Of course, it can also be used for entirely non-SMW purposes, whenever you want to do a large-scale replacement.
Currently it's only available in English, though translations should start coming in soon courtesy of Betawiki. You can read more and download it here: