I was a big fan of Meebo, personally. Since it was a web app, you could sign in once on any computer and all of your chat clients were there.
...Guess who bought it and killed it? https://en.wikipedia.org/wiki/Meebo
...Guess who bought it and killed it? https://en.wikipedia.org/wiki/Meebo
> In June 2012, Google acquired Meebo to merge the company's staff with the Google+ developers team.