I don't remember exactly how I got to it, but I opened a page (external possibly) that only showed the chat interface of Facebook. It was quite similar to the gabtastik screenshot
What I wanted was to create a Chrome Application shortcut for this page, and easily use Facebook chat as a side along application. However, I've not been able to find such a page. Is it possible to open the Facebook chat only interface directly (without using any third party scripts)?
Previously, once logged into Facebook, you could use the URL http://www.facebook.com/presence/popout.php — this no longer works (as of 12th October 2011) — or from any Facebook page chat (in the bottom left) → Options → Pop out.
The second option no longer works with the new Chat UI—18th July 2011.