There are many ways to give back and support WordPress and WordPress.com, as an experienced user or a coder and developer. The WordPress Forums are the first place to begin.
There are two support forums for WordPress.
The WordPress.com Forums are dedicated to providing help to WordPress.com users. It is staffed by Automattic employees who monitor and moderate forum posts but a majority of the support comes from volunteers, fellow users who want to give back and help others but also learn more about how WordPress works.
The WordPress Support Forums are for those using the self-hosted version of WordPress or WordPress MS (Multisite). This is mostly a volunteer support forum where experienced users help others get their questions answered.
WordPress.com questions will not be answered on the WordPress.org forum, and the reverse is true. Questions must be posted (and answered) in the appropriate forum section as well.