I spent a bit of time today redirecting all the old blog posts (from my local Community Server install) to their new location (custom domain on Blogger).
I eventually decided to stop the existing Community Server site and run a blank website in it's place.
I then used the free version of Helicon Tech's ISAPI_Rewrite to redirect all the old Community Server paths to the new Blogger location, a simple robots.txt refirect, and then threw in a wildcard redirect at the end to catch any other links (including comments that I didn't copy across).
It was actually quite easy to do in the end but needed to be done as adsense was still showing 10x more visits to the old blog as opposed to the new one. Also, since the fit of the new 100Mb line, I haven't had the port forwarded to the old server.
I'll run it for a while until all the search engines are updated and I can then finally drop my local server.
The product can be found here: