Added a new .stop() method which stops all animations running on the matched set of elements.

Example:
  $("#foo").slideDown(1000);
  setTimeout(function(){
    $("#foo").stop();
  }, 500);

src/fx/fx.js

@@ -368,6 +368,16 @@ jQuery.fn.extend({
 			if ( this.queue[type].length == 1 )
 				fn.apply(this);
 		});
+	},
+
+	stop: function(){
+		var timers = jQuery.timers;
+
+		return this.each(function(){
+			for ( var i = 0; i < timers.length; i++ )
+				if ( timers[i].elem == this )
+					timers.splice(i--, 1);
+		});
 	}
 
 });
@@ -466,9 +476,13 @@ jQuery.extend({
 			z.now = from;
 			z.a();
 
-			jQuery.timers.push(function(){
+			function t(){
 				return z.step(from, to);
-			});
+			}
+
+			t.elem = elem;
+
+			jQuery.timers.push(t);
 
 			if ( jQuery.timers.length == 1 ) {
 				var timer = setInterval(function(){

src/fx/fxTest.js

@@ -11,6 +11,29 @@ test("animate(Hash, Object, Function)", function() {
 	});
 });
 
+test("stop()", function() {
+	expect(3);
+	stop();
+	reset();
+
+	var foo = $("#foo")[0];
+	var h = foo.style.height;
+
+	$("#foo").slideUp(1000);
+	setTimeout(function(){
+		var nh = foo.style.height;
+		ok( nh != h, "An animation occurred " + nh + " " + h );
+		$("#foo").stop();
+
+		nh = foo.style.height;
+		ok( nh != h, "Stop didn't reset the animation " + nh + " " + h );
+		setTimeout(function(){
+			equals( nh, foo.style.height, "The animation didn't continue" );
+			start();
+		}, 100);
+	}, 100);
+});
+
 test("toggle()", function() {
 	expect(3);
 	var x = $("#foo");