PhotoDemon - Lightweight portable BSD licensed photo editor for Windows focused on performance and usability.
Bg Eraser - Background Eraser on Mac and Windows.
PhotoFlare - Quick, simple but powerful Cross Platform image editor.
ClippingMagic.com - Remove image backgrounds online. Make backgrounds transparent, white, etc. Edit, crop, rotate, fix colors, add shadows, all you need for great photos!
PixBuilder - Free Photo Editing Software for PC
Icons8 Background Remover - Quickly remove the background from any photo