web-adventures.org boasts a new web-based z-code interpreter, one that doesn't use Java, Javascript, or Flash. Instead, it uses traditional HTML forms and a page that refreshes after every command. The interpreter itself isn't directly available, but you can play a number of games with it at the site.
IFDB has gotten a makeover through the addition of custom styles. If you have an IFDB account (which is free), you can choose from user-submitted skins for the site. If you're really ambitious, you can make your own.
Spatterlight, Tor Andersson's all-in-one interpreter for Mac OS X, has been updated to the latest interpreters: Alan 3.0 alpha 5, Glulxe 0.4.3, Level9 4.1, and Scare 1.3.9.