Axosoft is a really interesting company and I've been using OnTime for a couple of years now.

They have just released a Chat Application, Single  User is FREE - Unlimited is on sale for $99

Visitors to your ASP.NET web site are presented with this simple and straightforward chat client. It's made to be super easy to use while also providing users with visual cues that help them follow the conversation.

• Depending on your preference, users can chat instantly or provide name and topic prior to chat.
• Color-coded messages: user, operator and system notifications
• Custom skins / logo images via simple css edits

• "Operator is typing..." indicator
• End-of-chat rating (optional)
• End-of-chat print / save options
• Opportunity to send an email in case an operator does not respond
• Send web page links

PureChat is written entirely with C# and javascript, against the 2.0 .NET framework. It uses Microsoft's ASP.Net AJAX, as well as selected controls from the AJAX Control Toolkit.