A perfect live chat system phpfreechat is quite a good little plugin,
giving you the option to have real time chat within a wordpress,

most other chat boxes we found were hosted solutions, meaning the chat box was ran by another website, and not contained on your own.
That sort of isnt the idea as far as I can see, if you have a chat box on your site, it would be a good idea to actually have the chat box on your site rather than on someone elses site, phpfreechat is one of the few that do this.

If you have any questions about Live Chat systems for wordpress, feel free to post a topic with your questions