In the last five years I have discussed an infinity of options that can be used to add a chat to a blog, from the simplest, like ajaxchat for WordPress, to the most sophisticated, like the meebo bar.
Here I leave you with an excellent list that they published a few hours ago on sixrevisions.com, I hope that one of the options is appropriate for your website.
This component allows each user to have their own avatar. The administrator can also give different privileges to different users, allowing to create a very interesting moderated community for discussion forums.
2. Meebo me
Meebo me is a product of Meebo.com, the famous instant messaging platform. This chat is compatible with Gtalk, AIM, Yahoo! Messenger and Facebook, so no separate registration is required and anyone can use their preferred chat client to communicate on our website.
JWChat is a script that only uses JS and HTML, being very fast in its execution and installation. It does not have great functions, but it is very useful for those who do not want anything too complicated.
CBox integrates into any website as a dynamic chat component that is very easy for anyone to use. The free version includes fewer features than the premium, although it is very valid for most current blogs.
5. Mibew Web Messenger
Mibew Web Messenger is free source, built with php and mysql and very easy to integrate into any website.
6. AjaxChat for WordPress
A small script made for WordPress users, allowing readers to participate in a chat without having to refresh the page.
7. AJAX Chat
It can also be used as a system to notify readers of any news. Any visitor will be able to leave a message in a few seconds, being ideal for those who do not want to complicate their lives with anything more sophisticated.
PHP-based chat that allows you to create separate chat rooms, send private messages and customize the appearance using CSS.
It uses the Google Web Toolkit and it looks like a desktop client. It offers a chat very similar to the one we have on Facebook.
10. Ajax IM
Ajax IM also has the free code and allows us to offer a chat at the bottom of our web pages, just like with Facebook.