Posterous (a free blog++ service that I love) announced yesterday that they were working to allow Ning users to import their blogs to Posterous. Look how many people have read this post! 13,000. Amazing.
Now, Posterous is not a Ning replacement, but if you have a Ning blog and want to save it, Posterous is a great place to house it.
Good luck, Ning users, I guess that all of my Ning hesitations are now paying off. I hate migrations.