Python stack
Languages:

Python 2 & 3

MVC-frameworks:

Django
Flask

ORM:

SQLAlchemy
Django ORM

Template engine:

HamlPy
Jinja2
Django template

Task queue:

Celery
RabbitMQ task queue

Asynchronus IO:

Gevent
Tornado

Messages:

RabbitMQ
ZeroMQ

Client-side
Specification:

HTML5 & CSS3

Script languages:

CoffeeScript
JavaScript

JS-frameworks:

jQuery
Underscore
Zepto
Atom

MVC-frameworks:

Backbone.js
Angular.js
Ember.js

CSS-preprocessors:

SASS
LESS

CSS framework:

Bootstrap
Compas
Flat UI
Foundation
960 Grid System

Test framework:

Phantom.js
Selenium
Jasmine

Task Runner:

Grunt

JavaScript stack
Languages:

CoffeeScript
JavaScript

Runtime:

Node.js
io.js

MVC-frameworks:

Meteor
Express
CompoundJS

Template engine:

Jade
Mustache
Underscore template

WebSockets:

socket.io

Deployment and Administration
HTTP servers:

nginx
Unicorn
Apache

OS:

Debian
Ubuntu
CentOS

Cloud platforms:

Amazon EC
Heroku
Nodejitsu

Virtualization:

OpenVZ
Xen

Name server:

BIND

Teamwork and testing
Revision control:

git
mercurial
svn

CI:

Jenkins

Bug tracking:

Redmine
Jira
Trello

Ruby stack
MVC-frameworks:

Rails
Sinatra

ORM:

Active Record
Datamapper

Template engine:

Slim
Haml
erb

Asynchronus IO:

EventMachine

Task queue:

Resque

Test framework:

RSpec
Cucumber

Database
SQL:

PostgresSQL
MySQL
SQLite

NoSQL:

MongoDB
Redis
CouchDB

Android
Languages:

Java

REST client:

Retrofit

Images:

Picasso

API
Social Media:

Facebook API
Twitter API

GeoTargeting:

Google Maps API

Calls and SMS:

Twilio API

Payment:

PayPal
Bitcoin