The problem with a lot of instant-messaging is the setup reqirements - software to download, registration, etc. A new site, Chatango tries to address these problems to enable ananymous chat via a flash movie within a html page. For example, I registered the name "gfxmonk". Now anyone can go to http://gfxmonk.chatango.com and just type into the litle box to chat to me without having to register.

On my side it's a little more complicated - I either have to have a webpage open all the time or I have a little notifier sitting in my system tray (which is the option I'm using at the moment). But all in all it's a great way to enable people to effortlessly contact you, without having to divulge their personal information such as their email address.