QuarterBukkit
An API extension for Bukkit, notably including special FX and particle/object system APIs.

QuarterBukkit helps finding and avoiding bugs and errors in your code, like accidentally accessing the Bukkit API in a different thread. Moreover, it provides a lot of APIs, in particular the FX ones, which internally take care of the dangerous job of accessing the CraftBukkit code, with you not even noticing that you've left the realm of pure Bukkit. Aside from those low-level wrappers, QuarterBukkit also comes with many other APIs, partly simple utility classes, partly complex and very powerful systems like the ObjectSystem API. Long story short, QuarterBukkit makes a lot of things easier and speeds up your development process by a fair bit.

There's no additional work for server operators because QuarterBukkit downloads itself from the BukkitDev, always check for updates, and even downloads new versions if they are available.

QuarterBukkit features:

You can find the source code and contribute to the source repository on GitHub. Visit the BukkitDev page for downloads which are verified by the bukkit team.