UPDATE: Xapian is now deployed for all users. Google search is now offered when Drupal search block is disabled. Details.

When the site gets too busy, the infrastructure team sometimes disables the built-in search function. When this happens, you can use Google to search by putting site:drupal.org in with your query. There are also a couple of unofficial sites mentioned in the comments below. The issue to discuss how best to handle providing an alternate search is here. Comments have been disabled on this post because they were becoming unproductive. If you are able to help with the problem, please do so via that issue. Please note that saying "someone" needs to do "something" will not be any more helpful on that issue. We are already well aware of that.

Michelle