I have been using Meebo as a chat client for over a year now to handle engineering and other subject related reference. One trick that I have added to my web 2.0 arsenal is using a two-edged, phone + chat, approach to reference:
Lets say I get a phone call or am handling general reference at our reference desk and get a phone call there. If I need to get a lot of information to the caller, and it just does not seem that telling them what or where the information is located is not working so well, then I will ask them to go to my profile here at the library on their computer. I then get them to scroll about halfway down the page and I can then send them textual information, web-links to information or databases. This phone-chat hybrid reference is a dynamite combination for explaining hard concepts or difficult situations.
I find that too often we spend a lot of time talking to people, who are already on the Internet, trying to point them to specific web-pages, waiting for them to get everything correct, spelling out web addresses, etc. It is much easier to just hand them the link that they need via the use of a chat client. We can give them more accessible information and do a better job of steering them to what they want this way. It seems less confusing. :)