If it is only to call to USA land lines then you have a better choice than skype = 1 cent / min with :
www.gizmoproject.com
and it work without your computer if you buy an adapter like grandstream.com
Gizmo uses the same aodio codecs like skype i.e.
iSAC & iLBC, so the sound quality is very good.
To call to Europe lycos phone may do the trick, one can get up to 2000 free minutes on their site.
But this software uses the codec G.723 when calling to land line phone, which is not the best choice about audio quality.
To call to France, Germany, UK … you can use
www.openwengo.com = 1 eurocent / min
but the server of wengo is often off i.e. quite buggy one. Normal, it is french made !
这个是我在skype别人给我的建议
比较有意思,没有尝试过
现在用的比较多的应该是Voip.ms吧