Liliko Chat is a fast and customizable Web chat system. It provides modern features such as desktop notifications, a responsive design, multiple languages and themes, and many more. Integration into existing community systems like phpBB 3 or MyBB is as simple as editing a config file.
NetIRC2 is an easy-to-use .NET IRC client library. It supports all major features relevant to making a chat client or bot. It has full support for synchronization contexts. You can use it from a Windows Forms or WPF GUI thread and chat events will be automatically dispatched, allowing you to completely ignore multithreading. It uses byte arrays internally, so mixed encodings can be handled. The IrcClient class can even be used as a component in the Forms Designer. Because it speeds up connect times with some IRC servers, an Ident server is included as well.
Ybot is erlang bot software inspired by Github hubot. It supports IRC and XMPP transports and is extensible with plugins. Plugins can be written with Python, Ruby, or shell. It supports IRC chat, XMPP multi user chat, and 37 signals Campfire chat. It can simultaneously run any number of bots on different transports.