Windows only: Free application XnView Shell Extension adds several image tools to your right-click menu so you can preview, resize, edit, upload, and convert images in just a couple of clicks. Made by the same people who brought you previously mentioned XnView—the lightning fast image editor and viewer—XnView Shell Extension brings many of the same great tools of XnView to your right-click menu. If you do a lot of work with photos but don't want to fire up a full-fledged editor for some quick resizing or converting, this context menu add-on looks like a winner. XnView Shell Extension is freeware, Windows only.
XnView Shell Extension