Tango Icon Library provides developers a set of professional high quality icons. They are in PNG ( Transparent background which can easily integrate into any web site) and SVG format ( Scalable which means you can increase the size of the icons without losing quality.
Requirements: Any Browsers
Demo: http://tango.freedesktop.org/Tango_Icon_Library
License: Creative Commons Attribution Share-Alike license
David’s Kitchen wrote an article: Scalable CSS Buttons Using PNG and Background Colors taught us how to create dynamic CSS Buttons using PNG, transparency and background colors that degrades nicely and supports full scalability.
It is really handy for developers because the length of the button will be changed according to the length of the text. The buttons are very pretty with Web 2.0 style. The color of the button changed if you hover on it. However, the buttons are not looking very nice in Internet Explorer 6.0, hope there is a version which supports IE 6.0 as well soon.
Requirements: Internet Explorer 6.0+, Firefox 1.5+
Demo: http://monc.se/kitchen/stew/buttons/btn.html
License: No License
