is awesome. You generate a font, then attach it and the Cufon.js to your site.
What you get is instant client-side text replacing. If done properly you won't even see the text popping to your Cufon font. Even better, it supports all but the oldest browsers (even works on IE6!)
1) use Cufon.now() at the bottom of the page above your .js scripts (like google analytics)
2) Older browsers w/out a css selector engine need the jQuery library loaded before cufon