Original Icons from the Crystal Clear[dead link] icon set (archived page as of 10 October 2012 at Internet Archive) by Everaldo Coelho. – The icons are licensed under the GNU Lesser General Public License (LGPL).
These icons can be downloaded in a single package at Open Icon Library.
You can also view these icons sorted by type.
All images’ real size is 128px in PNG format. For reproduced or derivative SVG work, see Category:SVG Crystal Clear icons.