Build Systems
Rebar
Rebar is a recent build system quickly gaining in popularity, although it has very little documentation at the moment. You can still see the system in action over the basho blog.
Sinan
Sinan is a build system designed especially for OTP projects and used by the Erlware projects. It allows to manage dependencies, retrieve missing packages, run unit tests and give code coverage metrics, do the actual compiling, run dialyzer over the code, etc.