Font replacement aka dynamic text replacement has been around since 2004. I did not start using it till late 07 but lately it seems to be a hot topic again. Mostly because it has become a lot easier to implement I believe and SEO has become more prevalent.
Which font replacement technique should you use?
I have been trying to find the best font replacement technique. I have not found a clear winner but font replacement can now be done just with JavaScript. It uses SVG or VML I believe to have the browser draw the font so to speak.
How font replacement works.
Currently I have been using cufon but not on this site. (I am using Flir now but not much longer.) It is strictly JavaScript which is nice no more setting permissions on the server or worrying if the gd 2 library is installed.
It is really easy to implement, and seems to more accurately render the font spacing and details then Flir aka Facelift Image Replacement.
Flir is a server side font replacement that uses php, and javascript to redraw an image on the fly of a font. It works really well but letter spacing does not work so great when you use smaller font sizes. Also there was a fairly bug that need to be patched a few months ago.
Other than that is great and is easier to use than sifr which uses flash to replace fonts. I am not a flash guy though so that may be why I have a bit of a bias towards Flir.
Typeface is another js font replacement tool. It does not use php and is very similar to cufon. You can read more about cufon vs typeface here. The best way to know is just to try. I have not used typeface yet but would be interested to hear your comments.
How to install and use Cufon
Below is a quick tutorial of how to use cufon, by Jeffrey Way of nettuts.com.
More Info:
For more information on font replacement go here to see 10 different techniques.