When the site gets too busy, the throttle module kicks in and search disappears for a while. In an effort to cut down on the number of posts reporting this, I am linking to all the recent ones here and promoting this.
When it's down, you can always use Google. Just put "site:drupal.org" in your query.
http://drupal.org/node/270417
http://drupal.org/node/272571
http://drupal.org/node/271612
http://drupal.org/node/269992
http://drupal.org/node/271694
http://drupal.org/node/271936
http://drupal.org/node/272208
http://drupal.org/node/270705
http://drupal.org/node/272506
http://drupal.org/node/255841
Michelle