TypeKit is a web service that allows you access to hundreds of fonts for your websites. I’ve just started using Typekit on my Android Icon blog, since I think that blog should use Droid fonts on as many platforms as possible (i.e. not just Android).
Android Icon is self-hosted (i.e. unlike Changing Way, it doesn’t live at WordPress.com) and so I can use plugins there. There’s a Typekit plugin, and I may well try it.
Typekit isn’t currently available at WordPress.com. I hope that it will be available soon.
Typekit would be good for WordPress.com, for those who blog there, and for Typekit. It would help WordPress.com profits by making the Custom CSS upgrade more attractive. It would help bloggers who want to use different fonts. For Typekit, it would bring attention and customers, some of whom would switch to paid versions of Typekit.