I have heard about it the first time in a FontShop newsletter I think, and now came across a site actually using it. Typekit lets you use designer typeface online on your website, so you don’t have to stick to the classics Georgia or Verdana and others anymore!

It uses Javascript to substitute the fonts of your website. It still might not be the best solution but it seems to work pretty well, the colymba.com blog now uses Adelle by TypeTogether for its headers.