What would we do without IM? There are a couple of people for whom that's really our only method of communication. Meebo has been my go to IM client for some time now. When I was an emerging leader Meebo was where my team held their meetings.
My local committees are just starting to get in on the action of chat based meetings.
I also like using Meebo as a virtual reference tool. Since you can embed a widget on almost anywhere, when it is front and center on your website visitors have an immediate connection with a real person and don't have to hunt down the service. (See sidebar.) Here's one library using Meebo for virtual reference.
Our kids know Meebo and so there's less of a barrier introducing that reference service to them than there is a more formal service that they have to fill out a form to use.