Those without an Xbox Live Gold membership can currently enjoy the core benefit--online multiplayer--free of charge. Microsoft has unlocked online play to all Xbox Live users for the next few days, which is excellent timing with the Star Wars Battlefront II open beta now live.
From now until Monday, October 9, at 11:59 PM PT (2:59 AM ET/7:59 AM BST), a Free Play Days For All event is active. This allows you to play games online on both Xbox One and Xbox 360 without paying for Xbox Live Gold.
One thing that is not included during this free trial period is Games With Gold. The free titles that Xbox Live Gold entitles you to are restricted to those paying for the service. October's Games With Gold freebies for subscribers include Oxenfree, Gone Home, and Rayman 3.