Because of jQuery’s architecture, other developers can use its constructs to create plug-in code to extend its functionality. Currently there are thousands of jQuery plug-ins available on the web that cover a wide range of functionality such as Ajax helpers, web services, data grids, dynamic lists, XML and XSLT tools, drag and drop, events, cookie handling, modal windows, even a jQuery-based Commodore 64 emulator. An important source of jQuery plug-ins is the Plugins sub-domain of the jQuery Project website. There are alternative plug-in search enginesthat take more specialist approaches, such as only listing plug-ins that meet certain criteria. The tutorials page on the jQuery site has a list of links to jQuery plug-in tutorials under the “Plugin development” section. This post features the best and most popular jQuery plugins from the year 2011.