Driven by the mocking of a colleague for never having done the stupid gruntwork of rewriting my old DasBlog-based permalinks, I stole Jon Udell's python code and ran it over the 8+ year history of Knowing.net. I think it mostly worked, although internal links between posts remain broken, since the DasBlog GUID-based identifiers have been lost.
I suppose I should now write a program to monitor the 404s and do manual fixups as traffic calls for, but I'm not even going to pretend that "I'll get to that in a couple days."
I apologize if this caused any spurious "There are 2100 new posts" messages from your newsreader.