CSS Deck – CSS snippet creation

http://cssdeck.com

JS Bin – Javascript tester

http://jsbin.com

JS Perf – Javascript performance tester

http://jsperf.com

JS Fiddle – Javascript snippet testing

http://jsfiddle.net

Codepen.io – Front End Developer Playground

http://codepen.io

Dareboost – Web page performance tool

https://www.dareboost.com/en/home

Bootply – a bootstrap friendly fiddle

http://www.bootply.com