StackBlur.js is a fast, almost Gaussian blur for canvas. It's based on implementation of StackBlur algorithm.
Vague.js is an experimental script that allows you to blur any kind of html element. Vague.js checks if the user’s device supports the CSS filters otherwise it can fallback using the SVG filters or the Microsoft css filters.
Spoiler Alert! is a jQuery plugin that hides copy and images with a bit of blur. Hint on mouseover, reveal on click.
Foggy is a jQuery plugin for blurring page elements. It supports IE (8 and up), Firefox, Safari and Chrome.
Foggy by default uses the "-webkit-filter: blur" CSS attribute. If the browser doesn't support it, Foggy falls back to a manual blur. It makes several copies of the selected HTML element. It adds transparency to all copies and moves each of them by small amount, thus creating the blur effect.