Prison servers fill a strange niche in the Minecraft world: players will, for reasons essentially unknown, willingly stick themselves in a structure or area which severely limits their activities, forces them to do manual labor, and often pits them against their fellow players for little clear reason. So, what possible appeal does the prison server concept have?
As it turns out, it holds a lot of potential for fun! Prison servers do limit the player at first, and while it may seem counter-intuitive, many of these prisons follow the same basic concepts as any RPG or MMO: grind up "levels" (usually a rank or designation in the prison), get better equipment, better living arrangements, and often a greater level of freedom. Many prisons also have an end-game of escape. Throughout the ordeal, players will battle both leveling and other players to advance themselves. Some go solo, but many form groups or "gangs" to further themselves, and divide the workload up while providing protection for their members from other prisoners.
Unsurprisingly, prison servers are very cutthroat environments, and are not for players looking for a casual experience. It takes resolve, skill, and determination to survive in these prisons. Think you can handle it?
Prisonmine follows the traditional model of prisons, and like most, uses its own set of custom plugins. This is a good place to start if you're after the basics of prisons, as it will give you an idea of how gathering resources, ranks, and PvP zones work in most prisons. While it doesn't stand out much from most prison setups, it is a great place for beginners trying to understand how the whole concept is done. Currently low-population, you will have an easier time carving out your name and legend here!
The Shank Tank is a role-play based Prison server. It includes a 31 rank system with access to a factions world upon completion of said ranks. The 31 ranks are divided into 3 wards A, B, and C. Each of these wards consist of a customized mine, Foundry, and animal farm. What separates Shank Tank from most other prisons is a heavily enforced RPG angle; prisoners and guards are expected to act as their characters at all times, whereas most prisons typically let players be "themselves", without having any particular backstory or purpose beyond playing.
SkyPrison is a somewhat different take on the traditional prison; as the name implies, it is up in the sky! Very similar to skyblock in some ways, each area of the prison is housed on its own island, and players can fly between them at will, provided they have access to a given island. It is well laid out, looks very nice, and the community there is pretty friendly. If you want a different take on the traditional prison, it's definitely worth checking out!
Remember, you can check out all of these servers and many more right here on the Minecraft Forum Server List! There are tons of servers to check out, and more are added every day. Enjoy!