#site-title {
	color:#303030;
	font-family:"Palatino", serif;
	font-weight:lighter;
	font-size:60px;
	float:left;
	position:relative;
	margin:0;
	text-transform:lowercase;
	text-rendering:optimizeLegibility;
}

That CSS does appear to work. I tested out the example you posted earlier, and that also worked for me. It's possible that *if* you had left one of the Fonts page selections in place, that was overriding your CSS before (I'm not sure what your settings were when you first wrote in). Please post another reply here if you are still having trouble.

Note: If the name of a font family is more than one word, it must be in quotation marks, like font-family: "Times New Roman".

From: http://www.w3schools.com/css/css_font.asp

I've been able to change the "menu" and "entry title" fonts on my own with little problem. What I don't understand is why, even when I change the font in the "Site Title" section, nothing happens?

I just want to be able to use a different font for my blog title and sidebar (date, categories, etc.) than for each individual posting. And all I want to use are very basic fonts: Tahoma and Palatino Linotype.

This is what my customized CSS looks like:

#site-title {
color:#000;
font-family:"Palatino Linotype", "Book Antiqua", Palatino, serif;
font-weight:bold;
font-size:80px;
margin:0;
text-transform:lowercase;
text-rendering:optimizeLegibility;
letter-spacing:-3px;
text-decoration:none;
}

But "Oswald," Helvetica, Arial, San-Serif is what shows up on my screen. :/