elevateZoom is a free Image zoom plugin with options for window zoom, inner zoom, lens zoom. Tinting and easing can be enables. It is distributed under GPL and MIT license.
jfMagnify is a jQuery plugin that creates a magnify glass effect. This plugin will magnify html content, not just images. Read more
MagnifierRentgen is a simple, lightweight, responsive magnifier hover plugin. (magnifying glass effect)
Zoomerang.js is a drop-in library that allows your users to zoom in on (almost) any element on your existing page. Read more
spzoom is a jQuery plugin to create simple hover image zoom. There are some options to custiomize width, height, position, Read more