example.js

var cloudmade      = new L.TileLayer.CloudMade({key: 'API-KEY', styleId: 997}),
    openStreetMap  = new L.TileLayer.OpenStreetMap(),
    openCycleMap   = new L.TileLayer.OpenCycleMap(),
    mapquestOsm    = new L.TileLayer.MapQuestOpen.OSM(),
    mapquestAerial = new L.TileLayer.MapQuestOpen.Aerial(),
    mapbox         = new L.TileLayer.MapBox({user: 'kkaefer', map: 'island'});

TileLayer.Common.js

// Lefalet shortcuts for common tile providers - is it worth adding such 1.5kb to Leaflet core?

L.TileLayer.Common = L.TileLayer.extend({
	initialize: function (options) {
		L.TileLayer.prototype.initialize.call(this, this.url, options);
	}
});

(function () {
	
	var osmAttr = '&copy; <a href="http://openstreetmap.org">OpenStreetMap</a> contributors, <a href="http://creativecommons.org/licenses/by-sa/2.0/">CC-BY-SA</a>';

	L.TileLayer.CloudMade = L.TileLayer.Common.extend({
		url: 'http://{s}.tile.cloudmade.com/{key}/{styleId}/256/{z}/{x}/{y}.png',
		options: {
			attribution: 'Map data ' + osmAttr + ', Imagery &copy; <a href="http://cloudmade.com">CloudMade</a>',
			styleId: 997
		}
	});

	L.TileLayer.OpenStreetMap = L.TileLayer.Common.extend({
		url: 'http://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png',
		options: {attribution: osmAttr}
	});

	L.TileLayer.OpenCycleMap = L.TileLayer.Common.extend({
		url: 'http://{s}.tile.opencyclemap.org/cycle/{z}/{x}/{y}.png',
		options: {
			attribution: '&copy; OpenCycleMap, ' + 'Map data ' + osm
		}
	});

	
	var mqTilesAttr = 'Tiles &copy; <a href="http://www.mapquest.com/" target="_blank">MapQuest</a> <img src="http://developer.mapquest.com/content/osm/mq_logo.png" />';

	L.TileLayer.MapQuestOpen.OSM = L.TileLayer.Common.extend({
		url: 'http://otile{s}.mqcdn.com/tiles/1.0.0/{type}/{z}/{x}/{y}.png',
		options: {
			subdomains: '1234',
			type: 'osm',
			attribution: 'Map data ' + L.TileLayer.OSM_ATTR + ', ' + mqTilesAttr
		}
	});

	L.TileLayer.MapQuestOpen.Aerial = L.TileLayer.MapQuestOpen.OSM.extend({
		options: {
			type: 'sat',
			attribution: 'Imagery &copy; NASA/JPL-Caltech and U.S. Depart. of Agriculture, Farm Service Agency, ' + mqTilesAttr
		}
	});

	
	L.TileLayer.MapBox = L.TileLayer.Common.extend({
		url: 'http://{s}.tiles.mapbox.com/v3/{user}.{map}/{z}/{x}/{y}.png'
	});

}());