programming languages

1. java

1.1. android

1.2. hadoop

1.3. spring framework

1.4. eclipse

2. python

2.1. youtube

2.2. instagram

2.3. google

2.4. spotify

2.5. dropbox

2.6. reddit

2.7. quora

3. javascript

3.1. run4tiger

3.2. tota11y

3.3. IBM design

3.4. histography

4. ruby on rails

4.1. ask. fm

4.2. we heart it

4.3. airbnb

4.4. funny or die

5. php

5.1. yahoo

5.2. wikipedia

5.3. flickr

5.4. wordpress

5.5. facebook (though they have their own php called HHVM)

6. objective c or xcode

6.1. every IOS app