I use Skype on occasion, but with recent editions it tends to run the CPU pretty hard even when idle. This is totally wrong, and makes it difficult to use other programs while voice or text chatting in Skype, let alone using Skype as a group VoIP channel when gaming.
This is a pretty common bug, it has been a problem ever since Microsoft took over Skype, and it appears that it is Microsoft-related: it occurs if you have set your default web browser to be something else than Internet Explorer. I use Google Chrome because, in my opinion, it is far better than Internet Explorer, thus I get the problem. If you use Internet Explorer, chances are you’ve not experienced this issue, however this does not in any way mean that Internet Explorer is the better browser.
To solve the Skype CPU problem, one solution is to set Internet Explorer as your default web browser. I’ve tried it, and it works. However, it presents the other and equally pressing problem that I do not want Internet Explorer as my default browser (or at all, if I could only get rid of it).
An intermediate albeit cumbersome solution would be to set IE as your default before you start Skype, then set your favourite other browser as default again immediately afterwards. Skype doesn’t mind this, it does the trick, but it is an extra load of work, and when I tried to present it to others they looked at me as if I was a madman.
The third and, probably, best solution is to assign the file types HTM, HTML, XHT and XHTML to Internet Explorer, but leaving your favourite other browser as default. This also works, and I can still use Google Chrome without a hitch. The only downside is that if you double-click on either of those four file types, it will open in Internet Explorer, but you can always right-click instead and select, say, Open in → Google Chrome, and I hardly ever have need for double-clicking on those files anyway.
Related link: Getting extremely high CPU usage on community.skype.com