We have started using Typekit. A huge list of typefaces to choose from. With the release of CSS 3 / HTML 5 and the use of the font-face tag, services like these will change the way we are currently designing websites.
I totally understand that there are many free alternatives, Typekit makes developing a site swift. When amending the site for an alternative typeface - this is updated in an instant. Where as, if I was to do this manually, I would be wasting at least 20-30 minutes of my time.
You make multiple kits and for each kit you get a few lines of code (<script ....>) and you paste those into your site. You select the fonts that you want in your kit, you select which elements you want to be displayed in the font and click save; all of this is done from the TypeKit website, it's not particularly difficult. And then just refresh your page and it will be updated.
So you only have to change your code once to add in the scripts.