Royalty free icons for web pages and applications

These sites offer icons for Web sites or applications, usable for free.

When the download link is not easily accessible, you can download the icons with the right mouse button and the menu command to save the image.
In some cases icons are provided in an exotic format and the image can not be downloaded, you can still use a tool to capture the icon you need.

PSD, SVG, BMP, ICO, ICON files formats are supported by GIMP that can save the images in any format. Xnview can convert a whole directory of PSD, BMP, ICO files.

Gray standard set	Gnome	SignalvNoise	Ginux (64)

Specialized icons...

Space Odyssey	Guitar	Chairs

More sets of icons...

• Humanity. Icons of task and computer objects in SVG files.
• Glyphicons. Black and white icons for buttons, lists, menus. Used by Twitter's Bootstrap.
• Token. Set of monochrome icons shared on Deviant Art.
• List of buttons and icons. With various licenses.
• Cartography. Restaurant, campsite and so on...

• Another list for icons from Commons.

Monochrome icons

If you want to make a "flat UI" interface, which has become the norm on mobile devices.

• Simple icons. In two colors but with different hues. The theme is social media and the web in general.
• Entypo. 250 pictograms for all fields in several image formats.
• The noun project. Search engine for icons.
• SVG Icons. A tiny code produces a big image.
• More SVG icons. Free under the MIT license. May be easily converted to PNG.

Another solution is to use a font for the icons, what Bootstrap does since version 3. These icons are best suited for image buttons.

• Icomoon.io. Vector icons generator. Thousands of icons are provided.