We always used to plug Finale Notepad as a free and well-equipped music notation software package. Unfortunately, Make Music have decided to charge for this product (only $9.95 though). So, what are the freeware alternatives that could be used on either Macs or PCs. One good looking alternative is MuseScore. This was mentioned recently on MusTech.net and there is a good review there. There is also a good comparison between Notepad and MuseScore here by David Bolton. So, thankfully, there are still open source solutions for a world dominated by Sibelius and Finale.
Unfortunately, there is no Mac install package, so you’ll have to revert to the Linux version at the moment.