(function() {
	window.EventUtils = {
		eventFuncs : [],

		addEvent : function(o, n, f) {
			var el, id;

			// Resolve element by id if needed
			o = typeof(o) == 'string' ? document.getElementById(o) : o;

			if (o.attachEvent) {
				// Since we can't use attachEvent we need to generate an unique id for the object
				// and place functions in an array one for each object
				el = EventUtils.eventFuncs;
				id = o._evtID;

				if (!el[id]) {
					// Generate new unique id
					id = o._evtID = el.length;

					// Add event listener old fashion way instead of attachEvent
					o['on' + n] = function() {
						var i, l, e = window.event, li;

						e.target = e.srcElement; // Force W3C style

						// Execute each event listener in order
						for (i = 0, li = el[e.target._evtID], l = li.length; i < l; i++)
							li[i](e);
					};

					// Create array with first function
					el[id] = [f];
				} else
					el[id].push(f); // Push in more functions

				// Fix the IE leak
				o = null;
			} else if (o.addEventListener)
				o.addEventListener(n, f, false);
			else
				o['on' + n] = f;

			return f;
		},

		removeEvent : function(o, n, f) {
			var i, li;

			// Resolve element by id if needed
			o = typeof(o) == 'string' ? document.getElementById(o) : o;

			if (o.detachEvent) {
				li = EventUtils.eventFuncs[o._evtID];

				if (li) {
					// Detach event listener by looking for it and remove it from the array
					for (i = 0; i < li.length; i++) {
						if (li[i] === f)
							li.splice(i, 1);
					}
				}
			} else if (o.removeEventListener)
				o.removeEventListener(n, f, false);
			else
				o['on' + n] = null;
		}
	};
})();

Example of an simple event class not using the unload event