OpenResty is a full-fledged web platform that integrates the standard Nginx core, LuaJIT, many carefully written Lua libraries, lots of high quality 3rd-party Nginx modules, and most of their external dependencies. It is designed to help developers easily build scalable web applications, web services, and dynamic web gateways.

Zabbix the enterprise-class open source network monitoring solution.

Telegraf is the Agent for Collecting and Reporting Metrics & Data

Puppet

Grafana The open platform for beautiful analytics and monitoring

Chef

Ansible is simple IT automation.

Jenkins

Virtualenv is a tool to create isolated Python environments. Since Python 3.3, a subset of it has been integrated into the standard library under the venv module. Note though, that the venvmodule does not offer all features of this library (e.g. cannot create bootstrap scripts, cannot create virtual environments for other python versions than the host python, not relocatable, etc.). Tools in general as such still may prefer using virtualenv for its ease of upgrading (via pip), unified handling of different Python versions and some more advanced features.

Django