Last updated June 18, 2012.
This section is the starting point for those who want to contribute by testing code. Even if you do not code, you can still help Drupal's development process by testing. There are many things to test for and ways to help! If you have not already done so, you can start by enabling the Contributor and Developer blocks in your Drupal.org profile (My account > Edit > Contributor link / Developer link). The #drupal IRC channel is a great place to get in touch with people who can guide you in getting started with testing.
Here are some great areas that are always in need of testing help.