Forums are plentiful out there. Flash forums exist in many languages and many sizes. There are high traffic forums and smaller ones where you can get to know the regulars. Whatever you're looking for, you'll probably find it.
Flash MX 2004 Forums: www.flashmx2004.com/forums
These forums are exclusively dedicated to working with Macromedia Flash.
Were Here Forums: www.were-here.com
A busy online community (forums) for Flash designers and developers.
Macromedia Web Forums (Flash): http://webforums.macromedia.com/flash/
Official Macromedia web forums. Also available in newsgroup format (news://forums.macromedia.com).
Flash Move: www.flashmove.com/board/index.php
An online community for Flash.
One of the biggest and the oldest, this established community is also probably the busiest.
Flash MX Files: www.flashmxfiles.com/phpBB2/
Busy forum with a wide range of Flash-related subjects.