The Linux Cookbook: Tips and Techniques for Everyday Use

Two particularly useful (at least for me) commands are removing numerous files or completely eradicating a given directory.

The quickest way to delete numerous files:
find /parent/directory -type f -iname '*jpg' | xargs rm -f

The quickest way to remove a non-empty directory:
rm -rf /directory

Additional usage examples.  Found a shell programming example.