Our library of free online slots covers all of the biggest software providers and the best new slot games in the industry. Below, we’ve narrowed down five of our favorite slots to play in demo mode for December. Eligible players in Michigan and New Jersey may choose from thousands of online slots at BetMGM, Borgata, and PartyCasino (only available in NJ). NJ players may also choose from about three dozen new online casinos, including bet365,…