Some of my great co-workers recently released a new icon font – Genericons
The details are in The Genericons Icon Font Story announcement post. In additional to being a nice general use icon font, it is licensed under GPLv2 (or later), so no more trying to sort out licensing terms to see if the icon font will jive with your existing open source projects. They are also free, as in no cost. The font is already in use in the new WordPress Twenty Thirteen theme ( demo site is at http://twentythirteendemo.wordpress.com/ ).
For more examples check out the bottom of the announcement post and genericons.com site.