GREEK HELMETS

Corinthian The Corinthian helmet was probably first developed in the 8th century BC. Each helmet was custom made for the man who was to wear it. It took a great degree of skill to fashion the helmet from one single piece of bronze. Early in the helmet's career there were two types of crests. One laid flush on the crown arcing from front to back. The other type was worn high, curling forward at the top. Around the 5th century BC we see representations of Spartans wearing crests transversely, arcing from one side to the other. This was probably a sign of high rank. When not in use, these helmets could be pushed back to rest on the head. This is the position common in Greek art as it allows the viewer to see a face. The helmet itself was very strong, but it had some serious drawbacks. The small eyeholes seriously impaired the wearer's vision and left him practically deaf. After the 5th century the use of the Corinthian helmet fell out of use in favour of more lightweight, open-face types.
Illyrian This helmet originated in the Peloponnesian in the 7th century BC. Unlike the Corinthian, the Illyrian was made in two pieces joined together at the crown. The crest always ran from front to back, flush to the helmet in order to help protect the seam. There were also two ridges running along either side of the seam to provide extra protection.
Chalcidian "Chalcidian" is a modern name referring to the type of vases on which this helmet is often seen. It was used mostly by the western Greeks and Italians. This took the basic form of the Corinthian helmet, rounded the cheek guards and formed openings for the ears. They often were made with ram heads embossed on the cheek pieces. The temple and forehead were also often decorated with relief lines.
Pilos This was a design which was based upon a leather cap (which was often itself worn under the bronze version). It became synonymous with the Spartans and was probably used well into the Hellenistic period, if not longer. It is possible that there were variations upon this design. Firstly, most were probably unadorned without either decoration or horsehair crests or plumes for the average hoplite. Junior officers may well have worn a crest with senior officers having a transverse crest - as they had previously on the Corinthian and other variants. Some units such as the Sciritai themselves may well have worn the leather or linen variations instead - especially after they became a hammipoi type of unit (probably after the Peloponnesian Wars). Some Pilos helmets might have had hinged cheek guards.
Petasus The petasus was a wide-brimmed hat worn to keep the sun away while working in the fields, travelling etc. This hat was also converted into a helmet. It was worn by horsemen and lt. Infantry in the 5th century. Interestingly enough, some of these helmets were covered in fabric to give the appearance of being nothing more than a cloth hat. 
Boeotian The Boeotian was especially favoured by the cavalry because of its great visibility. It was a popular helmet, used also by the Romans until around the end time of Republic.
Attic Developed in the late 5th century BC and used until 2nd century BC. With its open face and hinged cheek plates, it was less confining and offered better vision than the Corinthian.
Phrygian During the mid 4th century BC there was a return to more heavy armour. This Phrygian began showing up during this time and soon became the most common helmet used by the Macedonians and the Greeks.