17. Free vector icons: Retro Volume 1
This set of 120 vector icons by Vietnamese designer Min Tran presses all the right retro buttons. If you want more you can find Volume 2 right here, and there are plenty more icons to be found on his Dribble page.
18. Free UXPin icon set
UXPin's a collaborative wireframing app that's perfect for building prototypes quickly and easily, and to help out with the process the UXPin team has made this beautiful and diverse suite of over 80 icons, designed for web and mobile UI design, available to use for free.
Promising any icon in any format, size and colour in 20 seconds, Icons8 is a comprehensive collection of 76,100 free flat icons. With categories business, clothing, food and more, Icons8 lets users download icons as both a Mac App or ZIP file.
This vibrant collection of shaded vector icons from graphic resource Freepik is just one of the many sets they've curated. Perfect for businesses and independent projects, these icons are free for both personal and commercial use. Each set can be downloaded in an .AI, .EPS and .SVG format.
Rendered in simple black and white, this set of crisp vector icons mix functionality with emotive ideas. Besides standard icons for security and messaging, such as padlocks and envelopes, this collection from Iconfinder also features hearts and eyes to give your designs that personal touch.
22. 350 pixel perfect icons
An awesome set of 350 pixel perfect icons that are perfect for apps and websites. You can use then for both personal and commercial use and scale them to any size you need.
23. 80 mini icons
Featuring 80 pixel perfect mini icons available in both PSD and Icon Font format. These clean and elegant icons are small but perfectly formed.
24. Metrize icons
Here's fantastic resource for designers and developers – a free collection of 300 metro-style icons that you could use for your apps or web projects. They're all free to use in both personal and commercial projects and the download includes not only the PSD, SVG, ESP and AI but also the web font.
25. Chunky Pika Icon Set
Check out this Pika-style vector icons released by the Dutch designers at Dutch Icon. The set includes 42 chunky pixel-perfect icons that you can use for your next personal or client project.
26. 44 Shades of Free Icons
Need some simple icons for your next client project? Here's a set of 44 icons you can use. They're in a PSD format, enabling you to easily edit and adapt them.
27. Token icon set
Token includes 128 unique icon designs, available as an ICO bundling of 16x16px, 32x32px and 256x256px icons, or as a PNG at 128x128px. Each icon has both dark and light variants, and comes along with a PSD which includes the layer styles for each resolution.