The CSS Ninja has created a Font Dragr drag and drop font tester:

Font dragr is an experimental web app that uses HTML5 & CSS3 to create a useful standalone web based application for testing custom fonts, once you visit it for the first time you don’t need to be online to use it after the initial visit. It allows you, in Firefox 3.6+, to drag and drop font files from your file system into the drop area. The browser will then create a data URL encoded copy to use in the page and render the content in the dropped font.

Used in the app:

• HTML5
  • Offline access applicationCache
  • Drag and drop API
  • File API
  • contenteditable attribute set to true so the text can be edited.
• CSS3
  • Custom fonts with @font-face
  • Gradients
  • Rounded corners using border-radius
  • Drop shadows with text-shadow & box-shadow
  • Attribute and pseudo selectors
  • Multiple border colours
  • Box model adjust using box-sizing

See it in action:

Go to Source