I faced the same problem. Customers could submit a form and then multiple e-mail addresses will receive a mail message. If the response of the page takes too long, sometimes the button was pushed twice or even more times..
I tried disable the button in the onsubmit handler, but the form wasn't submitted at all. Above solutions work probably fine, but for me it was a little bit too tricky, so I decided to try something else.
To the left side of the submit button, I placed a second button, which is not displayed and is disabled at start up:
<button disabled class="btn btn-primary" type=button id="btnverzenden2" style="display: none"><span class="glyphicon glyphicon-refresh"></span> Sending mail</button>
<button class="btn btn-primary" type=submit name=verzenden id="btnverzenden">Send</button>
In the onsubmit handler attached to the form, the 'real' submit is hidden and the 'fake' submit is shown with a message that the messages are being sent.
function checkinput // submit handler
{
..
...
$("#btnverzenden").hide(); <= real submit button will be hidden
$("#btnverzenden2").show(); <= fake submit button gets visible
...
..
}
This worked for us. I hope it will help you.