I never played with Google Web Fonts before today so I asked Google how to use them in a Blogger blog and found a number of procedures; unfortunately, all of them updated the style of all posts on the blog. If you read the basic web font instructions provided by Google and you’re familiar with HTML and CSS, the snippet below should make perfect sense. Use HTML view to do something similar in your blog post.
<link href='http://fonts.googleapis.com/css?family=Cinzel:900' rel='stylesheet' type='text/css'/>
<div style="font-family: Cinzel, serif; font-size: 300%">
Hello, world!
</div>