From Lord Pixel (whose site doesn't render in Safari, bah!) comes the OS X only Unicode Font Inspection tool. There's something like this that comes with Windows, only nowhere near as slick. Among other things, this is the quickest way I know of to look up the codepoint for some odd character whose name I might not know.
It reveals among other things how Unicode-oblivious popular fonts like Verdana are:
Hmm, in a recent note here I used a character (ō) that doesn't seem to be in Verdana, which is what ongoing would like the browser to render it in if possible; but I see the character - is it auto-magically fishing it out of another font?.