Mobile and Responsive Testing
Here are some resources for testing responsive design and mobile
Multiple views of common responsive sizes on one page
http://mattkersley.com/responsive/
iPhone specific simulators - Nice in that it shows the chrome of the OS too and allows you to inspect the elements.
iPhone 4 Simulator http://iphone4simulator.com/
iPhone 5 Simulator http://iphone5simulator.com/
Android Emulator http://www.manymo.com/ (does not allow element inspection)