It should be noted that putting Helvetica <i>after</i> Arial in your stylesheet is self-defeating if your aim is to display Helvetica on Macs but Arial on Windows. Macs ship with Arial, so such declarations mean Helvetica will never be used.
Of the new fonts they recommend, I actually really like Calibri which is included in Vista, Office 2007 and Office 2008 for Mac.<p>I wouldn't rely on it solely as the safe assumption is only ~40% +/- 10 of your audience has it, but hopefully in time it will be a nice alternative. Not really a fan of Tahoma, too condensed for the screen in many cases.<p><i>Calibri is always described as a 'humanist' font, which I think makes it the kind of font you'd be pleased to take home to meet mother.</i><p>lol
Aside from Lucida Grande and Palatino Linotype which everyone already knows about, this list is unbelievably unreliable... perhaps based on their limited sample it would work, but not for any major site that gets visited by other users than just designers.
Good discussion, but I cannot wait for the day when this is no longer an issue: <a href="http://www.alistapart.com/articles/cssatten" rel="nofollow">http://www.alistapart.com/articles/cssatten</a><p>The @font-face property really needs to find its way into more browsers (IE, I'm looking at you!)...
Great news about improving probabilities of replacing tired standards like Times New Roman and Helvetica.<p>Hope they're right about this generalizing to the general population from their "heavily designer-weighted" samples.
A more in-depth article with a matrix of available font types:<p><a href="http://24ways.org/2007/increase-your-font-stacks-with-font-matrix" rel="nofollow">http://24ways.org/2007/increase-your-font-stacks-with-font-m...</a>
I was rather surprised to see Georgia missing, however I don't know about it's availability on the Mac.<p>I actually think Myriad Pro is becoming a web-safe font if your primary audience is designers - it's shipped with Photoshop after all.