What is "sbt"

Fairly fast, non-intrusive and easy to set up for simple projects
Configuration, customization and extension are done in Scala
Precise recompilation (in theory) is done using information extracted from the compiler
Continuous compilation and testing with triggered execution
Supports Scala/Java mixed projects, jars packages, generates documentation with scaladoc
Supports Scalacheck Test, Specifications and Scalatest (Junit is supported by a plugin)
Start Scala REPL with project classes and dependencies in classpath
Multi-module and support for external projects
Running tasks in parallel, including running the parallel test
Dependency management support: inline declaration, external Ivy or Maven configuration files, or management manual

Official repository on Github https://github.com/sbt/sbt.