Joomla 1.0.5 is now available for download at the offical Joomla web site. Joomla 1.0.5 is a Bug and Security Release, and it contains fixes for Security Vulnerabilities. The guy's at Joomla have advised it is highly recommend that you upgrade to the latest version.
You can download Joomla 1.0.5 in two formats the full package, which contains all Joomla! files and a patch package which contains only the files that have been changed by the Security work