WordCamps are short, 1-2 day conferences that focus on everything WordPress. They are designed to have both a general focus (on blogging, writing content, marketing websites and the business surrounding WordPress) and a technical focus (aimed at developers writing plugins and themes).
There are over 50 WordCamps every year held all over the world in over 40 countries, and are a great way to explore the community. Many WordCamp sessions are placed onto WordPress.tv, and is a great opportunity to help the WordPress community, either by speaking, volunteering, or sponsoring.
You can find out all upcoming WordCamps at WordCamp Central.
Contributor days, usually held after WordCamps (but can be independent), are events that are set up to help you contribute to WordPress. The benefits to contributing to WordPress are numerous, both for a business looking to get more exposure in and amongst the WordPress community, to lone developers looking to grow their skills working in a team on a massive project.
You do not need to be code proficient to contribute to WordPress. They are looking for a wide range of skills, like support, theme review, as well as accessibility.
Look at your local WordCamp if they are holding a Contributor day. Alternatively, if you're based in the United Kingdom, you can find the latest WordPress Contributor day at http://www.wpcontributorday.com/.
Local User Groups
.org Support Forums
WordPress Stack Exchange