ScribbleHere is a free live chat site. You can see a screenshot of the plugin below taken from my blog.

In ScribbleHere you create a chat page that you can always find at the same address, and then invite others to the page to chat with you. No one needs special software, just your web browser!
The ScribbleHere Wordpress Plugin is a way to add parts of the chat page, or anyone elses to your Wordpress blog. You can add two different parts of your chat page: the list of online users, and the posts.
There are two broad steps required to get the plugin on your blog. They are described below under two seperate headings.
In this step you will actually add the plugin to your blog page. You will need to know a little about HTML to complete this step properly. There are three different PHP method calls you can make to display three different views of a chat page. Here is a summary of the available method calls. If a method parameter has ”=something” this means that there is a default value and you don’t have to set this value if you don’t want too.
user list: scribblehere_users(chat_page_id, width=100%, height=300px, display_title=true)
post list: scribblehere_posts(chat_page_id, width=100%, height=300px, display_title=true)
combined: scribblehere_combined(chat_page_id, user_width=20%, posts_width=80%, height=300px, display_title=true)
Most of the method parameters are self explanatory, but the display_title parameter for each call simply says to create a title for each display that links back to the chat page so that people can click to chat.

Note: the chat page id is the number at the end of the web page address for the chat page you want to display on your blog. The picture above shows you where exactly the chate page id is.
You can find your theme template under the appropriate theme directory in the wp-content/themes directory. Most likely you will want to add the plugin to complement your blog in the header, or a sidebar.
Say you want to add the plugin to the top of your blog like I’ve done on my Wordpress blog. Open up the file called header.php and insert something like the following in the appropriate place…
<?php scribblehere_combined(25, '100px', '400px', '200px') ?>
This line tells your blog to display both the user list and posts for chat page 25. It says to make the user list 100px wide, the posts 400px wide, and the entire display 200px tall.