Tired of having to make cumbersome graphics out of the fonts you want on your website only to have to re-do them when something in the design or colors changes? Web designers have long wished for a way to promote more than just the standard, boring fonts in a page without resorting to tricky shenanigans and weighty graphics.
You can try it out for free through the Trial account which limits you to 5gb of bandwidth (the fonts are served from Typekit.com). It also requires that you put a Typekit badge on your site if you plan to keep using the fonts. Testing them requires nothing, however, but a signup.
Personal accounts start at 24.99/year and go up from there and have wider access to fonts in the Typekit library.
Overall, Typekit works well and is compatible and functional in the most popular browsers (IE and Firefox). You can also avoid the legal hassles of buying font rights to use them on a site, since these are already done by Typekit. Typekit is also much easier to use than sIFR or Cufon, the most popular font enablers up to this point.
Definitely worth a try.