jQuery

jQuery is a fast and concise JavaScript Library.

jQuery simplifies HTML document traversing, event handling, animating, and Ajax interactions for rapid web development.

Zotonic uses jQuery for all client side javascript programming.

Open Source

Webmachine

Webmachine handles the HTTP protocol for Zotonic. Webmachine is made by Basho.
MochiWeb

MochiWeb is an Erlang library for building lightweight HTTP servers.
Nitrogen

Nitrogen is an Erlang framework for highly dynamic web sites.
epgsql — PostgreSQL driver

epgsql Is a pure Erlang database driver for PostgreSQL.
Twitter Bootstrap

Zotonic's HTML is based on the proven Bootstrap framework, made at Twitter. Bootstrap is made up of simple and flexible HTML, CSS, and Javascript for popular user interface components and interactions.
ErlyDTL

ErlyDTL is an Erlang implementation of the Django Template Language.
jQuery

jQuery is a fast and concise JavaScript Library.
gen_smtp

A generic Erlang SMTP client and server framework that can be extended via callback modules in the OTP style.
erlang-oauth

OAuth library for Erlang.