potrace - Open source program that transforms bitmaps into vector graphics.
Vector Magic - Easily convert JPG, PNG, BMP, GIF bitmap images to SVG, EPS, PDF, AI, DXF vector images with real full-color tracing, online or using the desktop app!
DragPotrace - A GUI for potrace using Objective-C for OS X 10.11
SVGConverter - Free Online SVG converter software that converts your PNG, JPG/JPEG, BMP, TIFF, WEBP, PDF to SVG, AI, EPS, PDF.
Ras2Vec - Raster to vector conversion program for Windows 95/98/NT
Autotracer.org - Free online image vectorizer