Fabien Quatravaux

<a href="http://www.fontsquirrel.com/" rel="nofollow ugc">Font Squirrel</a> is your best resource for FREE, hand-picked, high-quality, commercial-use fonts. 
They provide a large part of their fonts in a web-embedding-ready way that is supported by all major browsers (@font-face CSS method).
The provided formats are : 
* TTF – Works in most browsers except IE and iPhone. 
* EOT – IE only. 
* WOFF – Compressed, emerging standard. 
* SVG – iPhone/iPad
They provide an API to list, preview and download fonts very easily : this unofficial plugin is using this official API.
When you browse fonts and dispplay one with this plugin, the font is downloaded from fontsquirrel.com. If you then choose to install the 
font, its css rule is put in the head section of you website pages so that you can use it on any page. The WordPress built-in editor 
(TinyMce) has a dropdown list that lets you choose the font you want for each part of your site.

Font Squirrel (unofficial)

Bring fonts from fontsquirrel.com into WordPress. Fonts kits are downloaded into your content directory and linked with @font-face.

Eric Alli

The Google Typography plugins allows you to use any <a href="http://www.google.com/fonts" rel="nofollow ugc">Google Font</a> for any text on your existing website without writing a single line of code. In the Appearance > Typography settings page, simply add and customize as many fonts as you’d like, then apply it to any existing HTML tag or CSS selector.

Google Typography

A simple plugin that lets you use and customize (in real-time!) any fonts from Google Fonts on your existing WordPress site.

Font Squirrel (unofficial) vs Google Typography