The definitive way for designers to test responsive websites.
http://www.dimensionsapp.com
Google Chrome Add on / Extension
https://chrome.google.com/webstore/deta … fehjbnmifk

Firefox Web Developer tool ( Control-Shift-M ) For Testing Responsive Website

Control-Shift-M in Firefox really comes in handy and saves a lot of time during web development.

Mapbox | Design and publish beautiful maps very good alternative to Google map
https://www.mapbox.com/

Create Your Own Web Map With Mapbox Tutorial
http://www.youtube.com/watch?v=b3o0-1Sga4k

Responsinator
Responsinator is a simple tool that shows your website at different sizes.
http://www.responsinator.com/

This one's pretty cool. You can see a five screen sizes at the same time.
http://mattkersley.com/responsive/