ShellTools is a collection of free Unicode-aware Windows shell extensions. It adds some new useful commands like Resize image*, Install/Uninstall/Load/Unload font, Copy size, Copy path, Show hidden files, Show file extensions, File note, Refresh icons etc to right-click menus in Windows Explorer.
ShellTools is freeware, it does not contain any ad-ware, spy-ware or bloat-ware. System requirements: Windows XP/Vista/7/8 (32/64-bit)
Control panel where you can show/hide any available commands, as well as specify advanced options like image sizes that are displayed in Resize image submenu:
Screenshots of context menu with some ShellTools commands visible. You can define in ShellTools options window what image sizes are available in sub-menu. By default resized images are saved to the same directory as source files, with added file name suffix, but you can choose different output folder when you hold down Ctrl key while selecting size from menu.