Amazon S3 downloads index.html instead of serving

If you are doing this programmatically you can set the ContentType and/or ContentDisposition params in your upload.

[PHP Example]

      $output = $s3->putObject(array(
          'Bucket' => $bucket,
          'Key' => md5($share). '.html',
          'ContentType' => 'text/html',
          'Body' => $share,
      ));

putObject Docs

If you are using Hashicorp Terraform you can specify the content-type on an aws_s3_bucket_object as follows

resource "aws_s3_bucket_object" "index" {
  bucket = "yourbucketnamehere"
  key = "index.html"
  content = "<h1>Hello, world</h1>"

  content_type = "text/html"
}

This should serve your content appropriately in the browser.

Edit 24/05/22: As mentioned in the comments on this answer, Terraform now has a module to help with uploading files and setting their content-type attribute correctly

Running curl -I against the url you posted gives the following result:

curl -I http://speakeasylinguistics.com.s3-website-us-east-1.amazonaws.com/
HTTP/1.1 200 OK
x-amz-id-2: DmfUpbglWQ/evhF3pTiXYf6c+gIE8j0F6mw7VmATOpfc29V5tb5YTeojC68jE7Rd
x-amz-request-id: E233603809AF9956
Date: Sun, 18 Aug 2013 07:58:55 GMT
Content-Disposition: attachment
Last-Modified: Sun, 18 Aug 2013 07:05:20 GMT
ETag: "eacded76ceb4831aaeae2805c892fa1c"
Content-Type: text/html
Content-Length: 2585
Server: AmazonS3

This line is the culprit:

Content-Disposition: attachment

If you are using the AWS console, I believe this can be changed by selecting the file in S3 and modifying its meta data by removing this property.