Arc to SDA v4.5 by Mark Rhodes (November 1987) - This handy utility will convert a collection of files compressed with Arc into a self-dissolving file.  The program goes much farther than converting .arc to .sda, it can also analyze the block allocation map for all the files on the disk.  The coolest feature I was never aware of is called "whittle".  Using whittle, you won't run into a situation where you give someone with a single disk drive a file so big it can't be uncompressed because there isn't room for both the compressed file and it's contents on a single floppy. Included in the archive is documentation describing many of the other features.

Note - there is a newer version of this program available here (v5.1).