dd_rescue copies data from media with errors. It also supports reverse direction copying, so you can approach bad spots on your media from both directions.
The dd_rhelp tool automates this.

gnu_ddrescue has superceded the functionality for dd_rescue's primary purpose:
Copying data in presence of errors. In many scenarios, gnu_ddrescue is easier
to operate than dd_rescue with dd_rhelp.

dd_rescue is still very useful for some special features such as the splice and
sparse copies, preallocation and secure overwriting with random numbers.

The plugins to dd_rescue provide real additional value:
* hash calculation while copying, optionally even S3 multipart style
* lzo (de)compression while copying
* (de/en)crypting files while copying

dd_rescue also features optional bandwidth limitations and writing to several output files.