OK, SandboxToys is now publicly available. See this thread.

IMPORTANT NOTE to the users of the version previously published in this thread:
I have modified slightly some things in the new version, notably the registry keys needed to launch some tools from the context menu of the files and folders in Explorer. To update the registry, it is necessary to repair or uninstall and reinstall SandboxToys. So, overwrite the old SandboxToys.exe with the new one, then use the Start Menu shortcut "Uninstall or Repair SandboxToys", and answer No to the confirmation dialog to activate the Repair option.
After the repair operation, you should see a new context menu function called "Open Sandboxed Container", available only on shortcut files (.LNK files.)