With the new forum software, I had the option of installing an integrated chat system. Additionally, this chat system can be injected to pages outside the forum. So I've thrown it onto the front page. If you're logged in to the forum (and then stay logged in through a cookie), the chat system will show you online and available to chat while you browse the forum or front page.
If it works well in practice, I'll probably remove the link to the old chat system that popped up in its own window and had a separate sign on.