After running through all of the other extensions I could find on here and not finding any that did what I wanted, I decided to take a chance with this.
First, the good: This does exactly what I wanted it to do - it hooks up to one of several IM accounts, and displays a customizable "Online" or "Offline" chat graphic on the web page that allows users to click to chat with you without needing to sign up for an account of their own.
Works like a charm, and it's quite a brilliant little piece of code.
On the other hand, I had to jump through about 50 hoops to get all the components and do the install. I had to: Sign up for AIM / Googletalk, sign up for the developer's site to download, click through a maze of pages on the site to get to the DL page, DL and install the Mod, modify my index.html file as per instructions, sign up for the Habla back end with a separate account, install yet ANOTHER piece of code on my computer to get my IM sessions to co-operate with each other... jeez.
One click install, please, and one account sign-up at most!