The use of iconography is very pervasive in presentations, infographics and data visualizations. The minimal, visual portrayal of concepts is quick and easy to understand and is often more effective than photos or complex illustrations. Below are many different sources of icons for your projects.
The Noun Project has a searchable library of over 1 million royalty-free icons submitted by designers all over the world. All icons are FREE to use if you give the designer credit in your final work, or the inexpensive NounPro plan ($39.99/year) gives you unlimited royalty-free licenses to download and use the icons. Plug-ins are available for direction integration with Microsoft Office, Adobe Creative Cloud and Google Docs applications.
The AIGA has made the complete set of 50 passenger/pedestrian symbols developed by AIGA is available for all to use, free of charge. Signs are available here in EPS and GIF formats. This system of 50 symbol signs was designed for use at the crossroads of modern life: in airports and other transportation hubs and at large international events. Produced through a collaboration between AIGA and the U.S. Department of Transportation (DOT), they are an example of how public-minded designers can address a universal communication need. First set of 34 symbols was published in 1974, and received a Presidential Design Awards; 16 more symbols were added in 1979.
Pictofigo images or in other words "Freehand Drawings" are now available to be downloaded from the Pictofigo website and to be used on making blogs, making presentations, developing project/process workflows, adding value to forums, contributing through articles etc. Free and paid plans are available.
Streamline 3.0 is a complete kit of 30,000 icons (in 53 categories and 720 subcategories) available as vectors for purchase and download. Each icon comes in three different weights: light, regular and bold. You can download a FREE sample pack of 100 icons.
All of Icons8 icons are free for personal use and also free for commercial use, but they require an attribution link back to their web site. They’re distributed under the license called Creative Commons Attribution-NoDerivs 3.0 Unported. A paid option is available to remove the attribution requirement.
The Orion Icon Library has over 6,000 free vector icons, that can be edited and downloaded as PNG, SVG or SVG Sprites. All of the icon designs are royalty free for use in both personal and commercial projects. There is no need to attribute or create a linkback when the icon designs are used in a personal project; however, you need to attribute our icon designs and add a required linkback when used in a commercial project.
Nucleo is a paid icon library of 27,500 vector icons combined with an icon library organizer application you can use to keep track of the icons you use in your projects. The application also allows you to customize the icon color, secondary color, line weight, cap styles and rotation before you drag & drop the icon into your application.
Iconfinder is a paid library of royalty-free vector icons. You have two options for purchasing icons: first, you can go with the Pay-as-you-go model and buy when you need icons or second, choose a Pro subscription where you get convenience and more downloads. Iconfinder also has a library of over 16,000 Free icons!
Material Design has made their library of 1,044 vector icons available free for everyone to use, and organized into 16 categories. Designed primarily for web projects and mobile applications, each symbol is available in five themes and a range of downloadable sizes and densities (Filled, Outlined, Rounded, Two-Tone and Sharp)