I am amazed at the quantity of music notation software available on the market. The two most popular products, Finale and Sibelius, get most of my attention. However, there are many, many more titles from which to choose. A wonderful comprehensive list of music notation products is available at:
http://ace.acadiau.ca/score/others.htm
If you peruse the extensive list of notation programs on this site, you will note quite a few free notation programs.

Finale NotePad 
The free notation program that I use most is Finale NotePadwww.finalenotepad.com. It is a free download and a lite version of Finale. Finale NotePad 2008 added step entry via MIDI making it a viable option to use to communicate with other programs, as it will also export files in MIDI format. For a complete list of the features check out:
http://www.finalemusic.com/Notepad/New.aspx

The only major problem with Finale NotePad is that files are not backwardly compatible in Finale format. So, for example, you can’t open a Finale NotePad 2008 file in an earlier version of Finale. However, you can download earlier versions of Finale NotePad by searching the downloads section of the Finale Notepad website:
http://www.finalemusic.com/store/search.aspx

Opening Finale Files in NotePad
Finale NotePad can open Finale files. This makes it possible to create a file in Finale and then have others open it for playback and practice in Finale Notepad. I also find that Finale NotePad is a good place to start when teaching students how to use Finale. There is a limited number of tools.

Once students have the hang of NotePad, moving to Finale is a snap. There are some excellent tutorials that ship with Finale NotePad. From the Help menu, choose Tutorials.

Another free program that I have used is Nightingale Light
http://www.ngale.com/index_04.html

How are you or your students using Finale NotePad?

What other free notation software have you found helpful?