I just added a post at the Skype for Linux forum (http://forum.skype.com/viewtopic.php?t=4017) requesting that Skype be ported to the Z (please vote!). However, I'm wondering if my hardware (SL-5500) can even handle audio in and out, that is, it doesn't have a built-in microphone, right? Is it possible to get internet telephony working on the SL-5500 without an external microphone?

I have used KPhone/Pi on my 5500 with a cell phone mic/earbud combo and it works great for VOIP.

You can also use a normal pair of headphones, speak into the left speaker and it will act as a weak microphone.

To use the cell phone mic/earbud I had to get a plug to convert the jack/socket size down.

if you get a converter though will it do input AND output at the same time?

It will if you get a stereo adaptor XD

I reccomend The Pokia Phone, and the Belkin Nokia Boom.