You might try the node-s3-client.
UPDATE: Available on npm here
From the sync a directory to s3 docs:
UPDATE: Added client inialization code.
var client = s3.createClient({
    maxAsyncS3: 20,     // this is the default
    s3RetryCount: 3,    // this is the default
    s3RetryDelay: 1000, // this is the default
    multipartUploadThreshold: 20971520, // this is the default (20 MB)
    multipartUploadSize: 15728640, // this is the default (15 MB)
    s3Options: {
      accessKeyId: "YOUR ACCESS KEY",
      secretAccessKey: "YOUR SECRET ACCESS KEY"
    }
  });
var params = {
  localDir: "some/local/dir",
  deleteRemoved: true, // default false, whether to remove s3 objects
                       // that have no corresponding local file.
  s3Params: {
    Bucket: "s3 bucket name",
    Prefix: "some/remote/dir/",
    // other options supported by putObject, except Body and ContentLength.
    // See: http://docs.aws.amazon.com/AWSJavaScriptSDK/latest/AWS/S3.html#putObject-property
  },
};
var uploader = client.uploadDir(params);
uploader.on('error', function(err) {
  console.error("unable to sync:", err.stack);
});
uploader.on('progress', function() {
  console.log("progress", uploader.progressAmount, uploader.progressTotal);
});
uploader.on('end', function() {
  console.log("done uploading");
});