skype and used to be pigeon, but now I use digsby. Digsby adds tweating to the mix, plus facebook. So is a step up from what I have personally had with pigeon.
Skype is wonderful, quality sound attached to video and chat. Use it so often.
I came across Digsby last week, installed it and set it up. Was working fine the first night. Gf rang me at work the next day to say the laptop was dying, was taking 30 minutes to boot. Spent hours at it when I got home, was hanging for ages with something using 100% of CPU, but not listed in Task Manager. After much googling came across a similar problem someone had which they tracked down to a distributed processing DLL.
Digsby has an option where they basically sell your spare CPU cycles when your machine is idle for other projects. I'd turned all those options off, but that seemed to be the problem.
Uninstalled Digsby and laptop was back to normal.
So approach with caution.