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.
You know that they don’t work well at all on Safari….
You mean they show up above and to the right of the link? Yeah… that happens in OmniWeb, too. If you hover over link in the sidebar, they show up fine. I’ll have to take a look at it…