Distel is concurrent/distributed programming extensions to Emacs Lisp, integrated with Erlang's distribution protocol for talking with Erlang code. It includes an Erlang integrated development environment for Emacs, written in itself.
Remote GUD mode for Emacs is a unique Emacs Lisp
rsh-gud.el that allows you to debug a program
running on a remote host, with sources on the
local host. It works via rsh.
A high performance, scalable database modeled after Bigtable.
A fast C++ matrix library with an API similar to Matlab's.