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!
Inkscape - Inkscape is a free, open source professional vector graphics editor for Windows, Mac OS X and Linux.
potrace - Open source program that transforms bitmaps into vector graphics.
Sketch - Professional digital design for Mac.
RasterVect - Professional raster to vector conversion program (vectorizer).
Adobe Illustrator CC - Adobe Illustrator CC is a commercial vector graphics editor.