What client tools are available to manage Amazon S3 and CloudFront?

I use CrossFTP Pro to handle Amazon S3 and CloudFront on the Mac, Linux, and Windows. It can handle the HTTP header metadata and log settings as well.

I use CloudBerry FreeWare. Easy to use, just like FTP software.

https://www.cloudberrylab.com/explorer/amazon-s3.aspx

Jeff Atwood mentioned S3Fox Organizer on his CodingHorror blog.

http://www.s3fox.net/

Using Amazon S3 as an Image Hosting Service

Cyberduck for Mac & Windows supports the full feature set of both S3 and Cloudfront distributions including custom origins. See http://trac.cyberduck.ch/wiki/help/en/howto/s3.