gistfile1.js

    grunt.registerMultiTask('s3deploy', 'deploy to S3 using awssum', function () {
        // dependencies
        var awssum = require('awssum'),
            fs = require('fs'),
            path = require('path'),
            aws = require('./settings').aws;

        var amz = awssum.load('amazon/amazon'),
            AmazonS3 = awssum.load('amazon/s3'),
            s3 = new AmazonS3(aws.accessKey, aws.secretKey, aws.accountId , amz.US_EAST_1),
            src = this.file.src,
            dest = this.file.dest,
            files = fs.readdirSync(src),
            deployDone = this.async(),
            count = files.length,
            defaults = {
                BucketName: aws.bucketName,
                Acl: 'public-read',
                ContentType: 'text/javascript; charset=UTF-8'
            };

        files.forEach(function ( file ) {
            var fileSrc = path.join(src, file),
                body = fs.readFileSync(fileSrc, 'utf8'),
                options = {
                    BucketName: defaults.BucketName,
                    Acl: defaults.Acl,
                    ContentType: defaults.ContentType,
                    ObjectName: dest + '/' + file,
                    ContentLength: body.length,
                    Body: body
                };

            grunt.log.writeln('Deploying ' + fileSrc);

            s3.PutObject(options, function ( err, data ) {
                if (err) {
                    grunt.log.error('AWS Error: Status Code ' + err.StatusCode);
                    grunt.log.error('Error Code: ' + err.Body.Error.Code);
                    grunt.log.error('Error Message: ' + err.Body.Error.Message);
                    return deployDone(false);
                }

                count--;
                grunt.log.ok('Deployed to '+ options.BucketName + '/' + options.ObjectName +
                    '; Status Code ' + data.StatusCode);

                if (count === 0) {
                    grunt.log.ok('Done deploying');
                    deployDone();
                }
            });
        });
    });