Joker the IRC bot is a PHP class designed for quick and easy IRC bot construction. This base class contains methods that can be executed from your plugins. It has built-in flood protection, timers, and a powerful plugin system that allows you to reload plugin classes on-the-fly, without restarting the PHP console or disconnecting from the network.
MOHA Chat is a chat solution which comes with a intuitive Web client and can run on most shared hosts. MOHA Chat consumes fewer resources on the server side and is fast on the client side. It uses AJAX to retrieve the chat messages and user status. The client polls the server at regular intervals. It currently supports only one-to-one chatting with the Web client. The Web client encrypts messages using a key unique to the client when sending a message to the server and vice versa.
NoxBot is a modular IRC bot that uses the platform independence of PHP. NoxBot is easy to use and features many commands that can be given to the bot over IRC. There are the many available modules. If NoxBot does not provide exactly what you need, then it can be easily implemented as a module. NoxBot tries to stay as RFC-complaint as possible. Some of its features include authentication, module management, a help system, multi-lingual support, timers, a storage system that separates modules, and many more.
Pandorabots Chat Bot Interface is a learning tool for implementing AJAX to communicate between the browser and a server. The chat bot interface communicates via XML with a free chat bot you create and host at pandorabots.com. The client script controlls a div that records your ongoing conversation. The final product is an embedded chat bot in your Web site.