Font Matrix
The lack of typographic choices available to web designers has been a problem for years. It’s easy enough to declare a font using CSS, but the problem is that the end user has to have that specific font on their machine. This inconsistency has led the development community to settle on only a small number of fonts that are installed on nearly all Windows, Mac, and Lunix machines.
The list just got a lot longer.
The brains behind 24WAYS (www.24ways.com) have compiled a list of fonts that are available on all major operating systems, and fonts which come bundled with popular software suites (like Adobe Creative Suite and Microsoft Office). Browsing this list is very encouraging, especially since most Windows users have a version of office installed. It’s also surprising the amount of font overlap between Windows and OSX, which accounts for nearly all casual computer users.
http://media.24ways.org/2007/17/fontmatrix.html

Using this list can help designers and developers create richer typography for websites, and usual, nicer fonts can be used, which will then revert to defaults if the user doesn’t have that specific font installed.
It’s also worth mentioning that there are some great advancements in web typography using technology like Cufon, and CSS @fon-face properties. Just make sure you have the appropriate rights to use embedded fonts.