Visily - The easiest and most powerful wireframe software for agile teams.
FastStone Image Viewer - FastStone Image Viewer is a fast, stable, user-friendly image browser, converter and editor.
PSD to Sketch Design Converter - Convert a Photoshop design to a layered Sketch file for free
IrfanView - IrfanView ... one of the most popular viewers worldwide.
Learn SpriteKit by Design+Code - Make a platformer iPhone game from scratch in Swift 4.
Photoscape - high quality photo editing software, that enables you to fix and enhance photos.