A walkthrough has been posted with instructions for building your own
Fedora based EC2 images (both S3 and EBS backed) on the Fedora Wiki:
As a part of this, appliance definition files have been added to the
cloud-kickstarts git repository fedorahosted.org
While the current plan is to move official Fedora image generation to
koji, we know that most users are not able to build images in koji. We
wanted to ensure that there was a process by which the community could
build EC2 images to meet their needs. As such, we will continue to
maintain the Fedora appliance definition files with each release. The
goal is to keep the appliance file as close to the official images as
possible (read stripped down), so that you can add what you need and not
worry about pulling in a lot of things you don't need. You can expect
the appliance definition files for each release to appear at roughly the
time of the alpha spin.
We welcome feedback, comments, patches, etc. on both the documentation,
and the supported appliance definitions.