IcoFX - IcoFX is an all-in-one solution for icon creation, extraction and editing.
Anima App - Design, get feedback, convert to code, publish, iterate.
IconsExtract - Extract icons and cursors stored in EXE, DLL, OCX, CPL files
Sketch Repo - Collection of resources for anyone who uses Sketch
JDraw - Open Source SF.net
Figma - Team-based interface design, Figma lets you collaborate on designs in real time.