Take a look at TurnKey Linux. We just announced free access to all AMI's (40), including Rails, Django, Symfony, LAMP stack, Drupal6, Joomla, Wordpress, File Server, Domain Controller, Torrent Server, Redmine, MediaWiki, Zimbra and many others.

Optimizations for EC2 include a custom developed mechanism (EBSmount) that auto-mounts EBS devices when attached, support for automating EC2 instance setup via user-data scripts, security updates installed on boot (prevents window of vulnerability) and an AJAX web shell and a rich web administration interface (over SSL).

Announcement: http://www.turnkeylinux.org/blog/maintenance-release

EC2 Details: http://www.turnkeylinux.org/docs/ec2