Wow, where should I start? There are a wide range of volleyball rules, but the rules all depend on who you're playing for.
One type of rule that isn't really common in the U.S., except maybe California, are the Spanish volleyball rules. This originated by the German game of Faust Ball and the Spanish started playing this when American Troops played volleyball in the First World War. Even though the first set of rules were made in 1896, the first Spanish Volleyball Federation wasn't founded until 1960!
As time went on the Spanish started playing beach volleyball and then finally moved to water volleyball. Volleyball is starting to finally increase with the Spanish, but I still think it's far from how volleyball is in the United States.
Then there's high school volleyball. For the most part, it is played the same across the states, but it may vary slightly. There's freshman, junior varsity (jv), and varsity volleyball. All three levels play by the same rules usually, but the skill levels vary. Varsity has the highest skill level, freshman is the lowest skill level and jv is somewhere in between. To to get better, you must train and work even harder than before, especially while in high school.
Depending on where you are coming from and the skill level, the rules may vary slightly or significantly, just to give you a heads up. Or even if you're just out there having fun, make up your own volleyball rules and see how the game goes with your new rules!