I really like using the Pictos icon font (http://pictos.drewwilson.com/ http://pictos.drewwilson.com/). This icon set has already been mentioned, but it should

I really like using the Pictos icon font (http://pictos.drewwilson.com/ http://pictos.drewwilson.com/). This icon set has already been mentioned, but it should be noted that there are 3 icon image sets and then the font. The font can be used as an @font-face font on your site, which is a lightweight and very scalable way to add icons to sites and webapps. Plus, having the font icon in Photoshop makes quick mockups so easy!