css-discuss is a mailing list devoted to talking about CSS and ways to use it in the real world; in other words, practical uses and applications.
CSS Creator maintains Web-based forums for CSS-related discussion.
comp.infosystems.www.authoring.stylesheets (c.i.w.a.s) is an unmoderated Usenet newsgroup intended for the discussion of Web style sheets.
The CSS Working Group publishes a weblog where we post announcements, discussion topics, and resolutions. Our blog is aggregated with several other CSS-focused streams on The Future of Style. We encourage you to join the blog conversation: you can post a link to your own blog post (or your entire blog post) on the CSS3 Soapbox, or you can ask us to pull in on-topic posts from your blog if you post regularly about the future of CSS.
Technical discussion about the CSS Specifications takes place on the publicly-archived firstname.lastname@example.org mailing list. (subscribe, post). Everybody can take part in the discussions on www-style, but please don't use this list for how-to questions. (Try one of the above forums instead.)