A tool to help you design crosswords by hand, though there are automated functions to suggest words, or even fill in grids.
You create a grid, add clues by hand, then use the cut and paste tools to transfer to a wordprocessing or other desktop publishing package. So a nice tool for education, if you're running a club magazine or parish newsletter, or similar use. You can transfer files in the semi-standard xpf format, supported by some other crossword-editing software.
There's also...