How do I connect a 3rd party XMPP client to Cisco's Jabber Video?

To save people time:

Cisco Webex Connect IM uses Jabber as its chat protocol, so Pidgin (or any Jabber client) should be able to work with it. Here’s how to configure a Webex Connect account in Pidgin:

XMPP protocol
    Basic tab
        Username: first part of your Webex username before the @domain
        Domain: the part of your webex username after the @ sign.
        Resource: blank
        Password: your Webex IM password
        Local alias: whatever you want to show up for you locally in
            the chat window when you send messages, such as your
            username, instead of the lengthy Jabber ID string
    Advanced tab
        Connect port: 5222
        Connect server: c2s.<your domain>.webexconnect.com

Jabber (and obviously Pidgin) has conference/chat room support, and so does Webex Connect via a custom conference server:

Buddies menu: Join a chat
    Account: choose the XMPP Webex account
    Room name: whatever you want, or a known existing one
    Server: conference.isj1.webex.com (should already be filled in)
    Handle: whatever username you want
Inviting people once in the room:
    Conversation menu: Invite
    Buddy: enter their email address. Should show a list of matching names to select and invite.

Source: http://csh.us/2012/07/09/pidgin-support-for-cisco-webex-im/