Product Tour is a responsive tour snippet, with a step-by-step guide to help users understand how to use your website.
Trip.js is a jQuery plugin that can help you customize a tutorial trip easily with more flexibilities.
jQuery TourBus is a jQuery tour/walkthrough plugin. It takes more of a toolkit approach than some of the alternatives that try to have focusing elements, auto-progress with timers and indicators and etc.
Joyride is an easy to configure jQuery site tour wizard. Joyride is extremely flexible and lets you take control of how people interact with your tour. It's absolutely free to use.
Chardin.js is a jQuery plugin that creates a simple overlay to display instructions on existent elements. It is inspired by the recent Gmail new composer tour.
Bootstrap Tour is a quick and easy way to build your product tours with Twitter Bootstrap Popovers. It's easy to use and has many options to customize.
Single.JS is a jQuery plugin that make it easy to create single-page websites to portfolios, presentations and more. Single.JS offers beautiful animations to transition sections and resizes automatically the images.