Another new feature in Mac OS 10.7 “Lion” is support for vertical text (竖排 / 豎排 / shùpái), that is, text running from the top of the page to the bottom. (Lion’s Chinese text-to-speech feature was discussed here.) Chinese was traditionally written vertically (see this Wikipedia article), as in the image below. You can see 三字經 (三字经 Sān Zì Jīng or “Three-Character Classic”) at the upper right of the page.
Vertical text is dead simple to implement in TextEdit (which is included with the OS): just go to the menubar and choose Format > Make Layout Vertical. The text will begin at the right side of the page and run from top to bottom.
Below is a screenshot of some of the San Zi Jing in TextEdit. In this case, I began with the traditional version, so it runs from the top right down to 義 yì. After the gap, the simplified version begins and runs to the corresponding 义 yì.
Support for vertical text in the OS does not mean that every app will be able to take advantage of it (remember how long Mac OS X supported Unicode before any of the big apps like Microsoft Word and Adobe InDesign did?). Right now, TextEdit is the most accessible, but see this useful [chinese mac] page.
If you want to read more of the San Zi Jing, Wengu has an online version viewable in either vertical or horizontal format (with pop-up vocabulary help and translations into English and French). Or listen to it read aloud here (Flash required. Also includes the text in simplified characters, pinyin, and English).