Homepage: http://nootka.sourceforge.net/
Short demo:

Some quotes from the official site:
Nootka site wrote: For what?
Nootka is an application to learn classical score notation. It helps to understand the rules of reading and writing scores and develops skills for playing and singing notes.
The application is free and open source.
It works under Windows, Linux and MacOs.
For Whom ?
If You read this, surely You will find something for You in it !
for guitarists - it was began writing for them - for beginners and for more advanced ones
for all that want to develop theirs skills of playing and singing scores
for all to develop musical hearing
for teachers to support a progress of their students
for teachers to measure progress of their students
for parents of students to help their children
Features
numerous settings to personalize for user needs and capabilities
accurate method for detecting sung and played sounds
different name-callings of the notes
support for scordatures
clefs (treble, bass and others) and grand stave
exam mode with different levels to registry Your progresses
levels creator with wide range of settings
Czech, French, Polish and Russian translations