meh, I'm surprised nobody mentioned imo.im which was the last universal messenger I used (well you could use Gtalk/Facebook within outlook.com chat panel, so I

meh, I'm surprised nobody mentioned imo.im which was the last universal messenger I used (well you could use Gtalk/Facebook within outlook.com chat panel, so I guess that would be very last) and which unlike Miranda, Trillian, QIP and likes (unpopular Pidgin mentioned here with very low user base on Windows) didn't require installation and worked in browser, so you could use it on work computer, which was major benefit