At the time of publishing Digg Reader doesn’t have a simple batch unsubscribe method. This is the source for a bookmarklet that adds a delete button to feed items. Get the bookmarklet here: http://jsbin.com/UdaK/1

gistfile1.js

(function()
{
  var subscriptionDelete = function(item, feedUrl, successCallback, failedCallback)
	{
		var data =
		{
			feed_url: feedUrl,
			_xsrf: $('[name="_xsrf"]').val(),
			traditional: true
		};

		$.ajax(
		{
			url: 'http://digg.com/api/subscription/delete.json',
			method: 'post',
			data: data,
			dataType: 'json',
			success: function(data)
			{
				if (data.status == 'ok')
				{
					successCallback();
				}
				else
				{
					failedCallback();
				}
			},
			error: function()
			{
				failedCallback();
			}
		});
	};

	$('head').append('<style>\
.injected-delete-feed-button {\
display: inline-block;\
float: right;\
min-width: 20px;\
height: 20px;\
margin-right: 10px;\
border-radius: 10px;\
font-size: 18px;\
text-align: center;\
}\
.injected-delete-feed-button:hover {\
color: red;\
}\
	</style>');

	$('#dr-subscription-list li.dr-feed-list-item[data-feed-url]').each(function()
	{
		var item = $(this),
			feedUrl = item.data('feed-url'),
			deleting = false;

		$('<span class="injected-delete-feed-button">&times;</span>').appendTo(item.find('.dr-feed-label')).click(function(event)
		{
			if ( ! deleting)
			{
				deleting = true;
				var deleteButton = $(this);

				deleteButton.html('&hellip;')

				subscriptionDelete(
					item,
					feedUrl,
					function()
					{
						item.remove();
					},
					function()
					{
						deleteButton.html(':(');

						setTimeout(function()
						{
							deleteButton.html('&times');
							deleting = false;
						}, 3000);
					}
				);
			}

			event.stopPropagation();
		});
	});

}());