A large collection of icons in SVG and PNG format for applications and services. Designed with personal dashboards in mind. Download only the images you need.
Select one of the Font Awesome icons. Pick a square size for it (the numerical value is always X by X). Pick a color. Download it as a PNG.
Google has open sourced their Material Design Icons Library. It includes icons in PNG, SVG, and CSS glyph formats for many devices, functions, and features. Spritesheets are included. The icons have a Creative Commons By Attribution-Share Alike v4.0 license, so feel free to download and use them.