Q:

Facebook chat only page

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. 

A:

An alternative method, is to use the Pidgin chat client instead. 
The settings you need are:

Protocol: XMPP
Username: [your current Facebook username] (see step 1)
Domain: chat.facebook.com

Currently, you’ll need a Facebook Username (ie, facebook.com/mikeknoop). 
Open up Pidgin, Click Accounts, then Manage Accounts.  Now click Add. 
Fill in the Basic tab with the following details:

Resource: [unused, you may leave blank]
Password: [your current Facebook password]

On the Advanced tab, make sure all SSL options are unchecked. 
Click Add.  You’re done! 

A:

I mostly use the mobile website http://m.facebook.com/messages
Besides the chat functionality of course, it gives me:

Cross platform access without being dependent on installation rights. 
No Facebook icon in my taskbar (annoying if you're working at consultancy). 
No Windows notifications when you have a new message. 
Quick access to my timeline notifications. 

Update 09-04-2015: As of 09/04/2015 Messenger is available on the web https://messenger.com/ 

A:

You can use Facebook's very own messenger webapp:
https://www.messenger.com/

As @Peter stated, you can already use a Multi-IM client.  Just wanted to point out that there are many already around:

Trillian
Adium (Mac only)
Pidgin

E.g.: in Trillian there's already a Facebook plugin integrated, so you just need to provide your username (and you'll see the usual Facebook connect pop-up where you have to login and grant access). 
You can check the very long list of (Facebook-chat-capable) multi-IMs here: http://en.wikipedia.org/wiki/Comparison_of_instant_messaging_clients#Multiprotocol_clients

