Teamspeak, ventrillo, xfire, raidcall, msn messanger(idk if people still use), aim(again not sure if people still use), yahoo messanger(not sure if people still use this either), and there are probably more chat programs to use. Though I honestly prefer skype as I only chat with friends/family and not arbitrary people and wouldn't really care if anyone had my IP anyways I can change it pretty easy.
Just want to point out, that is no longer entirely true.
And when's this supposed to be happening? I've been on Skype since that was posted and I don't think it's on yet.
Although I thank the OP for this post because now I'm gonna try Google Hangouts because surely anything is better than Skype at the moment XD
(btw I thought that Teamspeak / Ventrillo / some others, require purchase or rental of a server to run through... Maybe I'm confusing it with other services. Although I can vouch for how good TS is for latency, performance and audio quality)
I used to use TeamSpeak when I played with some acquaintances in Guild Wars and SecondLife. Not played GW in years now and SL just seems to lost a lot of its appeal over the years. Except Skype, I don't think I've heard of the other ones either. Don't use Google+ as much as I should. Can't recommend any others as the ones I used to know are no longer updated or maintained.