Meebo
In geekspeak, it's an IM unifier. In plain English, it's a one-stop shop for all your instant-messaging needs. Which is to say that Meebo puts all your IM clients — the individual programs that make instant-messaging services incompatible with one another — into one browser window. There's no need to download all the different apps (MSN, AOL/ICQ, Yahoo, Jabber/Gtalk) to your computer to have any and all types of IM conversations. Available in four dozen languages.