Audacity is a free, easy-to-use and multilingual audio editor and recorder for Windows, Mac OS X, GNU/Linux and other operating systems.
Functional Ear Trainer
Functional Ear Trainer is a critically acclaimed ear training suite containing two programs. Functional Ear Trainer Basic & Functional Ear Trainer - Advanced. Both programs are different from the traditional ear training programs...
MuseScore is a free cross platform WYSIWYG music notation program, licenced under GNU GPL.