Good Game Studios claims to have more than 109 million users of its free online games, and they certainly do offer a large variety of games to play. There are strategy games like Empire, as well as a poker table and more besides.
Basic play is free, and all you need is a web browser. There's nothing to install or download. Certain aspects of the games require payment, but there's plenty of free stuff to keep you amused for hours.
Check out www.goodgamestudios.com for access.