Useful links!

Biosonics:  http://www.biosonicsinc.com/

DIDSON:  http://www.soundmetrics.com/

Myriax (SonarData, Echoview): http://www.echoview.com/

HTI:  http://www.htisonar.com/ 
 
Simrad:  http://www.simrad.com/
 
Sonar5 (Helge Balk):   http://www.fys.uio.no/~hbalk/