Safari displays emoji perfectly: on web pages, in tabs, and in the titlebar (if emoji are used in a page title). This makes it unique amongst the main OS X browsers: Firefox displays them in the title bar but not in tabs or on the page, while Chrome displays them in tabs but not on the page. There's a screenshot on my blog where I discuss this in more detail (the blog posting is an example that can be used to test browsers).
I played around a little with encoding settings in Firefox and Chrome but couldn't fix it. Maybe others will have more luck.
One issue I'm not clear about is what's required on the web backend to display emoji. UTF-16 encoding? Does anyone know?[kirkmc adds: It even works here, with Geeklog. 😄]
Mac OS X Hints