"a file-based build system - it inputs a list of file changes and a directed acyclic graph (DAG), then processes the DAG to execute the appropriate commands required to update dependent files"

"a simple solution to local Continuous Integration". It's ghetto CI, basically, but that could be really handy for working with languages with immature toolchains.

"a simple build tool for Scala projects that aims to do the basics well"

"a popular dependency manager focusing on flexibility and simplicity". Sort of adds Maven functionality to Ant.

"a Python-based framework for configuring, compiling and installing applications. It is a replacement for other tools such as Autotools, Scons, CMake or Ant."

"a build system designed for scalability and portability. It uses a syntax similar to make utilities you may have used, but it features many additional enhancements"

yet another Ruby CI solution

a pure Python replacement for a myriad of shitty build tools