IcoFX - IcoFX is an all-in-one solution for icon creation, extraction and editing.
Sketch Repo - Collection of resources for anyone who uses Sketch
IconsExtract - Extract icons and cursors stored in EXE, DLL, OCX, CPL files
Build with Sketch - Free LEGO-like kit for Sketch
JDraw - Open Source SF.net
Icon Slate - Icon Slate lets you easily compose, import and export desktop icons in many formats.