NoCheatPlus

Introduction
NoCheatPlus attempts to prevent cheat clients from exploiting weaknesses of Minecraft or its protocol, making your server more safe. Checks cover a wide range of issues including flying and speeding, fighting hacks, fast block breaking and nukers, inventory hacks, chat spam and other types of malicious behaviour. For a more complete list have a look at the Features Page.

Recommended
The following plugins might be useful to have a look at.

CompatNoCheatPlus (cncp)
Make plugins like mcMMO or MachinaCraft more compatbile with NoCheatPlus. Don't forget MagicSpells (TODO). Phasing out cncp, in favor of out of the box support within NoCheatPlus directly.

Orebfuscator
Orebfuscator fights all sorts of X-ray-hacks by altering the map information that is sent to the players, such that they have to mine blocks to actually reveal what is behind. Virtually a "must have".

ProtocolLib
Enable NoCheatPlus to process packets. Helps NCP to reduce false positives for some check, some checks can only run with processing packets (e.g. AttackFrequency, SoundDistance).
Downloads and History of Changes

• BukkitDev staff approved versions on the Files page.
• Releases at SpigotMC.
  
• Development builds at Jenkins.
• Do not download from any other source, do not use jars other people send you. (Unless you really know what they're doing.)
  
• Changes by build number can be examined in the Jenkins changes list.
• Build infos contain a somewhat digested view on selected builds.
• Notable builds for a quick overview of NCP vs MC version.
  
• All commits can be seen in the GitHub commit history.