I've been using Skype for quite a while, for both Skype to Skype calls as well as Skype to land line calls (mostly to the UK). I've recently come across an alternative to Skype called Gizmo which is pretty similar to Skype although it does offer some additional features. One feature that Skype currently does not offer is the recording of your Skype calls. At the moment, you have to use something like hotrecorder to record Skype calls, but if you use Gizmo, it comes with the software built in, which will make life easier if you are into recording your online conversations/conferences for use in podcasts.
I suspect that Skype will be coming up with something like this soon, although I haven't heard anything about it yet. For a comparison between Skype and Gizmo, check out this link.
Here is a quick comparison of call out rates of Skype vs Gizmo, and it looks like skype is cheaper than Gizmo at the current time (all amounts are in South African currency):
Skype:
SA land line: 44c
SA cell: R1.51
UK land line: 14c
UK cell (general): R1.63
Gizmo:
SA land line: 51c
SA cell: R1.64
UK land line: 19c
UK cell: R1.85
[Please note that these prices were accurate at the time of writing - by the time you read this, the costs may have changed, so please check their respective websites]