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.
superseriousstats is a small and efficient program for creating a Web page with statistics from various types of IRC logs. It keeps track of its parse history and only processes new activity before storing any accumulated data in a SQLite or MySQL database. It is suitable for high volume IRC channels and large log archives, and is relatively easy to integrate with IRC services (e.g. bots) that interact with the database and provide last seen information and many other statistics directly in your channel.
php Free Chat is a simple, fast, and customizable chat server that uses the filesystem for message and nickname storage. It uses AJAX to smoothly refresh and display the chat zone and the nickname zone. It supports customized CSS stylesheets and a plugin system that allows you to write your own storage routines.
dxirc is a easy-to-use yet capable cross-platform IRC client. Among its notable features are flexible configuration, a fully customizable look independent of system-wide settings, multiple server support with optional automated joining of selected channels, and the ability to connect via SSL.