I'm not sure how far back this goes, but on Leopard at least, pressing Option-Space on the US or US Extended keyboard layouts inserts a non-breaking space (U+00A0) rather than a normal space (U+0020). This might be useful for some people; unfortunately there seems to be no simple shortcut for inserting non-breaking hyphens on either of these two keyboard layouts.
Mac OS X Hints
http://hints.macworld.com/article.php?story=2008031611584277