Free open source software for two-way acoustic interactions with dolphins and other cetaceans using underwater whistles.
The blog, including the User Guide: http://leafyseadragon.blogspot.com/
The c2h project page on Sourceforge and the link to the downloads: http://c2h.sourceforge.net/
It works on most computers with Java 5 (free from Sun Microsystems and Apple Computers) and basic audio interface.
See the above links for details.