Light posting recently as I've been up to my neck in developing a new site. In the process I found a great little utility application that can be used inside any website. It's called SayBox and is very similar to an instant messaging application like AIM. While I wouldn't recommend it for everyday external IM communications, it would be great for an internal site where there is project work going on or where you need to kick a quick message over to a colleague - or client, or anyone else involved in a project. A good example might be the sale or acquisition of a business where you are collating documents into a website repository for sharing among colleagues. You could all be acting remotely and remain in easy contact. The beauty of SayBox is you don't have to fire up another app if it's already in the web application
This is one of an exploding class of lightweight applications that can be tacked into any website with the addition of a single line of code. The app is free (isn't that the best part) so there are some limitations on the number of messages you can store and it's not a fully fledged IM program. But for most purposes, the limit (300) is more than enough.
Try it out-I really like it.