I recently discovered font icons and I have to say I simply love them!
The benefits of using them are amazing, they are easy to resize without losing quality, and using CSS you can easily style the opacity, shadow, colour and when browser support gets stronger the gradient also using background-clip.
Chris Coyer gives an awesome tutorial on how to use the correctly on css-tricks here.
There are a number of free font icons available for use on the web or you can simply create your own in illustrator, save your icons as SVG and use a service like icomoon to create your icon font.
As they are loaded as a font in your CSS it cuts down on HTTP requests and saves on file size over image sprites so these will be especially useful for when you need to design for reduced bandwidth or a mobile site.