Meebo

Meebo is a website that allows you to use 5 different messenger services at the same time (google talk, msn, yahoo, aim, & meebo). The tool is AJAX based, and once running consolidates all the information so that you can be signed in to all 5 services at once, and work off 1 buddy list.

This is an example of web 2 point 0h because it simplifies and consolidates your instant messaging in one single program accessible from anywhere and because it is a great way to have your messaging capabilities on machines where program installations are regulated (i.e. bu computer lab).