ManageDsk is a small tool which allows :
- Create a empty .DSK file (in DATA format),
- Add some files in an existing .DSK file,
- Extract some files from an existing .DSK file,
- Rename some files contained in a .DSK file,
- Delete some files contained in a .DSK file,
- And since version 0.15, Read/Write DSK files from/to a 3,5" floppy
You can find it here : Amstradeus
In the download section : Download
Linux port
Sid made a port of ManageDSK to Linux and other UNIX OS. This port is command-line only but features all the important functionnalities for managing DSK files.