Boone B. Gorges, an independent WordPress and BuddyPress guru, has just announced his first stab at a data importer to get your Ning users setup inside of WordPress.
As of right now, it does not have any BuddyPress-specific functionality. But the data that it does import â€“ display name, username, email address â€“ are enough to populate at least the beginnings of a BuddyPress profile. The next thing to add is the auto-import of certain profile fields. I might try to do this tomorrow.
To stay up to date with the progress of this plugin, be sure to check back here or to his blog for more details.