I just needed to compress and encrypt some files on Mac OS X. The following command does that:

zip -ejr TARGET SOURCEFOLDER

This will ask for a password (twice to confirm it), encrypt and compress the sourcefolder and put it into a file named target (and auto add the .zip extension).

To unzip it do this:

unzip SOURCE -d TARGETFOLDER

This will ask for the password, decrypt and uncompress it into the targetfolder.