If anyone's curious, I've whipped up a quick XML dump filter tool, which can take a MediaWiki XML backup dump and filter it by title, based on a regular expression match or a file with a list of pages to take.
I used it to split up the Wikisource dump to move pages with their edit histories from the old Wikisource wiki to the new language-specific subdomain wikis (import of these dumps going on right now).
It's in C# (gasp horror) and runs on Mono. I haven't tested it on Microsoft .NET, but it probably runs there.
Source is available in the mwdumper module in CVS. No binaries or documentation at this time, but I expect to continue working on it for use in creating republisher-friendly dumps in the future.
-- brion vibber (brion @ pobox.com)