home | Word Processors/Screenwriting on the Mac
TextEdit - Free with Mac OS X, fully functional text program even though it is a quite simplistic. One big drawback might be that you don't have the ability to scale the window size up so it's easier to read. It reads in Word files and can output RTF or plain text (no formatting, bold, etc.).
Microsoft Word - Expensive, industry standard and offers you all of the formatting features you are accustomed to on Windows. You'll be able to share your files in Word format very easily and you can also zoom the windows 150%, 200%, etc. so that it fills screen to your liking. Reads and writes Word .DOC and RTF files.
Mariner Write - A very good, inexpensive alternative to Word. Opens Word .DOC files and can output RTF files. See the website here http://www.marinersoftware.com/sitepage.php?page=12 It has what you're looking for, simple formatting and zoom to full screen. You can download and use for probably 30 days before paying. $50 for download version.
Mariner Montage - same company makes a new alternative to Final Draft. It's a new Screenwriting program, so not as feature-rich as Final Draft, but a reasonable price, $140 for the download version. You could actually get this and Mariner Write for $200 in a bundle with their other programs Calc (like Excel), MacJournal and some Poetry program. See the website http://www.marinersoftware.com/
AppleWorks 6 - from Apple, cheap but a lot of features. It's comparible to Microsoft Works, where it comes with a spreadsheet program, graphics, database and word processor. They've replaced this with iWorks I think, but it's still around and a pretty good deal. http://www.apple.com/appleworks/ purchase it for $80 on the Apple Store online.
iWork 08 - great package includes Keynote (much better than Powerpoint), Pages (a powerful word processor and layout program) and a brand new spreadsheet application called Numbers. Pages will open and save to Word files as well as support RTF files which may be all that you need. Keynote reads and saves to Powerpoint documents. Finally, the new program Numbers is not as powerful as Excel, but contains 95% of the tasks that most of us use. It reads and saves to the Excel file format. Look for a 30-day trial at Apple.
Final Draft - Is available for Mac, but it's rather expensive. If you used it before, maybe the company can give you a deal on switching your copy from Win to Mac. http://www.finaldraft.com/
Mellel - I haven't used it, but have heard great things about this word processor. Maybe you could try the demo for 30 days. If you like it, it's only $50. Go here http://www.mellel.com/