Here’s an easy way to unrar many archives at once into a specified folder.

Requires the command-line version of unrar to be installed. If you already have the excellent app UnRarX installed, you can use the unrar executable that’s included in the app instead if you want. Just replace unrar with /Applications/UnRarX.app/Contents/Resources/unrar.

find /Volumes/Path/To/Rar:ed/Content/ -name ‘*.rar’ -execdir unrar e -o- {} /Volumes/Path/To/Un:rared/Content/ \;

I find this especially useful to extract multiple episodes of a specific TV series for use with Plex, for example:

find /Volumes/Path/To/Rar:ed/Content/Name.of.TV.Series.S01* -name ‘*.rar’ -execdir unrar e -o- {} /Volumes/Path/To/Un:rared/Content/ \;