They are all still used in forces today. All the pics are from the USN just to show that they are still used.
Is a helmet, shouldn't really need to elaborate but it is meant to protect the wearer from harm and worn mostly in combat situations.
Is called a wheel cover or peaked cover- used mostly for more ceremonial or formal occasions. ( http://www.dcmilitary.com/storyimage/DC/20110603/NEWS07/706039995/AR/0/AR-706039995.jpg )
Is called a garrison cover, worn for less formal situations, usually day to day when you might be in an office environment or be going in and out a lot, can be easily held or tucked into your belt. ( http://www.usmilitariaforum.com/uploads//monthly_12_2010/post-18845-1293769983.jpg )
Looks like a version of a forage cap. Basically it is a soft hat which can be worn in the field and still has a brim to shield you face. Basically it is what is warm in most battle dress uniforms in modern forces besides a helmet. ( http://4.bp.blogspot.com/_KUJ7I7dJy2Q/TUnwuO35bWI/AAAAAAAADtE/HROmk3BN0I8/s1600/Mullen+NWU.jpg )
Rank would then be visible by what decorations either on the brim, or what pins/patches are on the cover.