The latest this week was the acquisition of Favorite Peeps by slideshow creator Slide. Favorite peeps is a fairly simple apps that lets users display their favorite friends, providing their own details about them. It's a nice complement to Slide's TopFriends app.
With Facebook's new platform, thousands of applications are being developed. There will be a bit of a land rush as people strive to gain exposure to their apps.
The confusion of what apps are worth installing creates opportunities, particularly for companies who can package together bundles of apps. Going forward, I think there will be a need for a site to emerge (think Tucows or CWS Apps List) which will help users navigate and select Facebook apps.
What's most interesting to me is the speed at which this new Facebook ecosystem is emerging.