Rod VE3SOY did a demo of the JT65 digital mode at last night's meeting. This was the subject of an article by Steve Ford WB8IMY in the April 2011 issue of QST. For more information on JT65, see the JT65-HF project on SourceForge. Although the project page says it's open source, only Windows binaries are currently available. Discussions on the JT65-HF Google group suggest that it may be possible to run the Windows program on Linux using Wine.
Clock synchronizing is a must as the JT65 mode is very tight on timing and also frequency stability. Rod recommends Dimension 4 for Windows users.
JT65 links