Thanks to Kitta at kitta.net (whose blog I discovered today, by way of Matt Mullenweg), I've found an implementation of nicetitles that works with OmniWeb 5 (and thus Safari)!
It's gray and standard right now, but I might play around with the colours and background a bit if I feel creative. 
Kitta also provided a link to Dunstan's Easy CSS Drop Shadows, which I plan on using.
(I found the links on her Colophon page, for anyone who's interested.)
EDIT: If you try and download the files for the CSS Drop Shadows (located at http://download.1976design.com/dropshadows/), it downloads a file called "index.html" (at least in OmniWeb). I figured out that it's actually a ZIP file, so just rename it and add a .zip extension.
