Here are some forums that are related to web design and development. Note that many of these forums has many sub-forums that cover a large range of topics in many areas such as HTML, Flash, Photoshop. The topic listed are just my impression of their main topic overall forum.

General Web Design and Development Forums

• Sitepoint.com
• Pixel2Life.com
• TutorialFx.com
• Ozzu.com
• DevShed.com
• pxleyes.com
• WebsitePublisher.net
• CreativePro forum
• WebmasterGround.com
• Webmaster-talk.com
• WebmasterAds.com
• WebDesignerForum.co.uk
• LayersMagazine.com
• PhotoshopCafe forum
• FireworksGuruForum.com
• TalkDev.com
• FreeHostForum.com
• WebDigity.com
• TutorialGarden.com

Freelancer Forums

• TalkFreelance.com
• FreelanceGossip.com

CSS Forums

• CSSCreator.com
• WeLoveCSS.com
• Css-Discuss.org - not really a forum, but a discussion list

Wordpress Forums

• Wordpress Support Forum
• Sempre Fi Web Design Forum
• forums.LesterChan.net - Wordpress
• Content Management System forum on Sitepoint

Flash Forums

• Kirupa.com
• ActionScript.org
• FlashKit.com

PHP Forums

• PHPFreaks.com forums
• Killersites.com forums

Application Specific Support forums

• vBulletin.org
• SimpleMachines.org
• Adobe.com support forums
• PayPal Developer Community
• Zen-Cart.com/forum - ZenCart
• phpBB.com
• OSCommerce.com
• HostMonsterForum.com
• oswd.org
• LibraryCopyright.net
• forums.phplist.com
• Joomla.org
• Drupal.org
• JoomlaHacks.com
• JoomlaShack.com
• forums.mozillazine.org
• Coppermine-Gallery.net
• JoomlaContentEditor.net