Excerpt from the Rakefile in my Octopress install, showing how I use s3cmd for deployment to S3.

gistfile1.rb

desc "Deploy website via s3cmd"
task :s3 do
  puts "## Deploying website via s3cmd"
  s3_bucket = '<your bucket here>'
  ok_failed system("s3cmd sync --acl-public --reduced-redundancy public/* s3://#{s3_bucket}/")
end