A sampling of some free, online, and easy-to-use mobile device emulators that can help get you started with testing.
A free, customizable tool to test your website on any screen size, including desktops, tablets, televisions, and mobile phones.
A handy tool to check the appearance and functionality of your responsive web page for any arbitrary screen dimensions.
Mobile Phone Emulator
Used to test handsets like iPhone, Blackberry, HTC, Samsung, etc.
mobiReady is a free testing tool for mobile web developers, designers and marketers to evaluate a website’s mobile-readiness using industry best practices and standards.
From the article Beginner’s Guide to Mobile Application Testing, by Nancy Ratnakar