A list of some of the the best and most active webmaster message boards and support forums:

Actionscript.org Forums - Help with Flash

Affiliate Marketing Forum - Very active affiliate marketing forum. A few affliliate program managers hang out here.

CSS Forum - The CSS forum is a Cascading Style Sheet learning resource for web developers and designers.

Digital Point Forums - Internet Marketing and Search Engine Forums.

Domain Name Forum - Domains and websites for sale.

Dreamweaver Webmaster Help Forums - A place to learn and improve your webmaster skills.

FlashMXFIles - NON-PROFIT FLASH COMMUNITY FORUM

Hoover Web Templates Forum - Discuss support issues, search engines, cool sites or anything web design related.

JimWorld Forum - Search Engine Marketing Forum.

PayPal Developers - Developer Support Forum

SEO Chat Forums - Search Engine Optimization Forums

Sitepoint Forums - community in which webmasters can ask for help with topics such as site design, site programming, web hosting, site promotion and running an online business. (Also a good source for web design books.)

WebFrustration - Solutions to your web building problems.

Webmaster Talk - Coding Web Design, Hosting Domain Forum.

Webmaster World - News and Discussion for the Independent Web Professional.

Web Pro World - The World's Forum for eBusiness.