Uxcel - The easiest way to learn UX/UI design
Notism - What's next after wireframes? Visual Design and Notism.
prodmgmt.world - Quickly find product & UX techniques to get unstuck
Invision - Prototyping and collaboration for design teams
Design Skill Tests by Uxcel - Prove your UX design skills to colleagues and employers with Uxcel’s Skill Tests.
Red Pen - Red Pen lets you upload your design, share a short URL, and get live, annotated feedback super-fast.