If you're looking for an easy to use yet extremely powerful Ajax chat solution, then ASP.NET Ajax Chat may be just what you're looking for.

The software is simple to install, fast and customizable.

It uses AJAX to smoothly refresh (no flicker) and supports multiple rooms, private messages, moderation (kick, ban), customized themes based on CSS and much more! Developed using ASP.NET and AJAX technology Our powerful AJAX approach combined with Microsoft's ASP.NET provides a most powerful combination to deliver a reliable and scalable app, which is light weight and extremely simple to use.