I would start with pingomatic, and, if you want to avoid duplicates, go through the list on the Codex and compare it with the list of URLs Pingomatic pings. It’ll take some work, but I think that’s the best way to do it. Once you set your update services, I’d back up the list, so that if you either want to create a new blog, or something goes wrong with the normal one, you’re set. I hope this helps.
