SlotsUp.com provides the full list of slot machine games available online since the first online slot launched. All the games are divided by types, there few of them: Classic Slots (the oldest), Video Slots (most popular), 3D and HD slots (next generation slots).
Each game on site comes with the:
1) Technical information (like # of reels, paylines, min & max bet, casino software, etc.)
2) Slot machine game features (like Wild Symbols, Scatters, Free Spins, Bonus Games, etc.)
3) Free Demo game (Flash or HTML5-based)
4) Mobile version (if available)
5) Casino list (where the game can be played)
Currently website hosts 1853 free slots, but the number grows each day.
The main site version is on English, but there will be 3 more language versions available during the 2016.