Classy icons crafted according to Microsoft guidelines. Available in PNG and SVG. Free for a link
Feather Icons - Simply beautiful open source icons
Time Sink - Time Sink helps you track how you spend your time on your Mac.
IconStore - Free icon packs by first-class designers
ChatterBlocker - ChatterBlocker is the prime software to reduce the nearby conversation’s distraction that allows you to focus on your work.
Flat Icons - 20,000 unique, customizable icons with free lifetime updates
Strict Workflow - Enforces the Pomodoro time management technique by blocking distracting sites