Figma - Team-based interface design, Figma lets you collaborate on designs in real time.
Creative Market - Buy and sell handcrafted, mousemade design content like vector patterns, icons, photoshop brushes, fonts and more at Creative Market.
Sketch - Professional digital design for Mac.
SocialSizes - Sketch templates for sharing images & videos on social media
Invision - Prototyping and collaboration for design teams
Headers.me - Create social cover images that get you followers