If you want to modify your site with a custom font, using cufon is a way to do so.
To implement it in MT5, do the following:
First go to http://wiki.github.com/sorccu/cufon/usage
Read it fully.
Download the YUI-compressed version of cufón.
Generate your font script and download it.
Upload it to your server in the site name folder *to find this go to Design, Templates when you are on your blog/page. There highlight over the C-> icons and it will show your path.
Get the code such as:
<script src="cufon-yui.js" type="text/javascript"></script>
<script src="Myriad_Pro_400.font.js" type="text/javascript"></script>
<script type="text/javascript">
Cufon.replace('h2', { fontFamily: 'Myriad Pro' });
</script>
Modify HTML HEAD in the template under modules.
Add the script there before the licensing.
Then go back to your content and hit update/publish.
Worked for me!
Note the IE issue in step 4 of the cufon usage, I put in Banner Footer at the end:
<!--[if IE]>
<script type="text/javascript"> Cufon.now(); </script>
<![endif]-->
Reported on Movable Type 5
You might want to write this up into a more formal documentation article and submit it.