Cincom's Product Evangelist, James Robertson, has put together a basic Connection to the Facebook API. It's available on an "as-is" basis, and should load cleanly into VW 7.6, VW 7.7, ObjectStudio 8.1, or ObjectStudio 8.2. Developers utilizing this code still need to visit the relevant Facebook pages and acquire the appropriate application credentials themselves. There's a short summary page on the Facebook Developer Wiki as well.
To get started, login to the Public Store Repository and load the bundle named "FacebookBundle". From there, you can have a look at the following screencasts to get started:
If you prefer a simple web page based walkthrough, try this short tutorial post - it should get you going. Feedback, suggestions, and any contributions are welcome! Either email James, or just publish your additions back to the repository.
The Facebook Connect has been used for a client application already: There's a plugin available for BottomFeeder that imports the facebook activity stream into the news reader as if it were an Atom or RSS feed. It also supports posting new items back to Facebook, and commenting on items in the stream. If you are using BottomFeeder, check for updates - make sure you get the "BottomFeeder" update first, then get the Facebook plugin.
One further aside - I'd be more than happy to see this code ported to other Smalltalk implementations. If you're interested in doing that, please let me know - I'd like to keep the baseline code unforked.