I wanted to touch on two Facebook apps this afternoon that are highly useful for people with a lot of friends. One is to keep an eye on them, while the other is simply a means of extending your presence on multiple networks at the same time.
The first is called Unfriender, and it's been kicking around since last month. Once installed and given access to your data, it'll keep an eye on people you've added as friends and let you know if they've removed you as a friend later down the line. As a reason for creating the app, Unfriender's creators noted that all social services will let you know when someone's added you as an online buddy, but none will tell you when you've quietly been nixed. The closest thing on Facebook is when people change their relationship status, but even that information can be kept from the public eye with basic privacy settings.
The second app is fresh as of this morning and comes from the folks at Fuser (coverage). Once installed, it sets itself up as a secondary friends wall (the likes of SuperWall, et al) that can link up to MySpace and port over whatever comments are there. It also displays any photos that have been attached and limits the roll of comments to five at a time. The beauty of it is that it blends in with your existing wall and the rest of Facebook to look just the same. Couple that with MySpace Link and MySpace Mail, and you'll never have to leave the safety of Facebook again. Short of OpenSocial integration, this is probably as close as you'll get to accessing all of MySpace from the big blue.