ここ で書いた複数ファイルのdrag and dropは
http://www.appelsiini.net/2009/10/html5-drag-and-drop-multiple-file-upload
を参考にしたのだけど、微妙にmultipartのboundaryの作りが間違っているぽくて、
修正が必要だったのでメモっておく。
PHPではあのまま動くのかもしれないけど、少なくともrubyのcgiじゃだめでした。

修正版は以下。

1function upload(event) {
2
3    var data = event.dataTransfer;
4
5    var boundary = '------multipartformboundary'   (new Date).getTime();
6    var dashdash = '--';
7    var crlf     = '\r\n';
8
9    /* Build RFC2388 string. */
10    var builder = '';
11
12    var xhr = new XMLHttpRequest();
13
14    /* For each dropped file. */
15    for (var i = 0; i < data.files.length; i  ) {
16        var file = data.files[i];
17
18        /* Write boundary. */
19        builder  = dashdash;
20        builder  = boundary;
21        builder  = crlf;
22
23        /* Generate headers. */            
24        builder  = 'Content-Disposition: form-data; name="user_file"';
25        if (file.fileName) {
26          builder  = '; filename="'   file.fileName   '"';
27        }
28        builder  = crlf;
29
30        builder  = 'Content-Type: application/octet-stream';
31        builder  = crlf;
32        builder  = crlf; 
33
34        /* Append binary data. */
35        builder  = file.getAsBinary();
36        builder  = crlf;
37    }
38
39    /* Mark end of the request. */
40    builder  = dashdash;
41    builder  = boundary;
42    builder  = dashdash;
43    builder  = crlf;
44
45    xhr.open("POST", "upload.php", true);
46    xhr.setRequestHeader('content-type', 'multipart/form-data; boundary=' 
47          boundary);
48    xhr.sendAsBinary(builder);        
49
50    xhr.onload = function(event) { 
51        /* If we got an error display it. */
52        if (xhr.responseText) {
53            alert(xhr.responseText);
54        }
55        $("#dropzone").load("list.php?random="    (new Date).getTime());
56    };
57
58    /* Prevent FireFox opening the dragged file. */
59    event.stopPropagation();
60
61}

ついでにrubyでは

1cgi = CGI.new
2cgi.params["user_file"].each do |file|
3  do_something(file)  
4end

でok。

そしてこれを貼り付けるために
http://www.nslabs.jp/rb2html.rhtml
を改造して導入してみた。なんか今週末はコードばっかり書いてるなあ。