Windows: JDContextMenu is a small application that adds a variety of useful shortcuts to the right-click context menu in Windows.
None of the shortcuts are things you couldn't do within Windows with a few extra clicks or with a small third-party app, but JDContextMenu bundles them together into a small menu with one-click ease. You can copy the full filename to the clipboard, alter the time and date stamp of a file, run an MD5 checksum to verify file integrity and create new folders — the new folder tool allows you to create a variable number of numbered folders in a series.
Have a favourite shell extension of your own? If you've got the perfect tweak for your Windows context menus, we want to hear about it in the comments. JDContextMenu is freeware, Windows only.