Some years back internet-users were pretty much tired of using over and over again the same fonts like Verdana, Arial or Georgia.
Happily Mide Davidson came up with sIFR (Scalable Inman Flash Replacement) a mixture of Flash, Javascript and CSS to render headline fonts as images. Drawback at that time was low bandwith. Rendering of headline images often took too long. For a second the website looked somehow naked.

Today bandwith speed is much higher and perhaps it´s time to give image replacement techniques a new chance?
Webdeveloper Cory Mawhorter recently presented his PHP and Javascript based image replacement script named FLIR (Facelift Image Replacement) on facelift.mawhorter.net.

Currently FLIR is beta. It is available for free and can be downloaded from the download page.
FLIR is pretty well documented. If you intend playing around with it, read though nettuts.com comprehensive tutorial on how to use FLIR. Below the tut you can find some interesting comments on sFIR and FLIR.

For sFIR you certainly need Flash but can mark and select the headline-text. For FLIR all you need is the script but you can not select the text with the cursor which seems to me beeing the biggest drawback right now. Concerning SEO, both techniques put the headline-text into their correct html tags.

Keep in mind, FLIR is still beta but works already quite well on f. e. brokesanity.com/blog.

If your CMS of choice is Textpattern you can use a plugin (zem_ir) for image replacements. WordPress users can check out the FLIR plugin by 23systems.net.