How can I run dos2unix on an entire directory?

If it's a large directory you may want to consider running with multiple processors:

find . -type f -print0 | xargs -0 -n 1 -P 4 dos2unix 

This will pass 1 file at a time, and use 4 processors.

find . -type f -print0 | xargs -0 dos2unix

Will recursively find all files inside current directory and call for these files dos2unix command