I use Noteworthy Composer. It is not free though there may be a demo version, there was when I started using it. I bought it because it was so useful, it was about $30 or so at the time. It is intuitive, easy to learn, full featured, though of course short of a Finale or Sibelius.
I hear great things about Musescore. I have tried hard, and found it impossible, but people I respect use it and swear by it. It may be one of those imprinting things, I just got used to one way of doing it and can't reverse it.