From now through December 31, Internet phone solutions provider Truphone is offering a Facebook Platform-compliant "Call Me" button
You don't need a Truphone account to use this service.
At the core of "Call Me" is a moveable button that can be placed anywhere on Facebook that accepts attachments.
Once enabled, "Call Me" users who are also Facebook members can:
You can find the downloadable "CallMe" by logging into Facebook and then going here.
There's even a YouTube video of how to set "Call Me" up on Facebook.