Few weeks back Google has announced the availability of Google Fonts Directory. Google has now added an option to preview text with Font Previewer. With this option, you can preview text before embedding the code, you can edit the sample text, change text size and spacing, capitalize the text, add underlines and shadows. It lets you browse all the fonts available via the Google Font API. All fonts in the directory are available for use on your website.

Google Font Previewer

There are pretty good options to preview fonts like size, transform and decorations. You can also set the letter, word and line spacing for your fonts.

Google Font Preview [Via Google Operating System]