I could only find one program to do SSTV in Linux. That program is QSSTV. QSSTV is able to send and receive different SSTV modes using a Soundcard (PTT via serial port). For those who don't like to make a interface between the Soundcard and their tranceiver, there is an alternative way to get the sound where it had to be:

Using a Microphone and headphones !

It's really amazing what kind of results you can get with this. it's really simple: Here is a link to the the QSSTV project page: http://users.pandora.be/on1mh