It seems we have an uncomplicated and high-quality voice chat solution for SecondLife now:SecondTalk!

I went to get SecondTalk and had a first voice chat with my new friend Gomem, an English podcaster by the way:

Want to give it a try, too?
You need the newest Skype version 3, which allows voice conferencing for up to 10 users (if not even some more - one should test that.)

Then go to one of the (so far) 3 kiosks where SecondTalk is distributed.
http://www.secondtalk.com/get-second-talk/.

The German version of this post contains instruction how to use SecondTalk, but I can probably spare me that here in the English post, because in SL it is all well explained on the notecards attached to SecondTalk.