I haven't found much on the web regarding U.S. Navy uniforms, but there is some information available. The following site has published the 1905 Uniform Regulations for enlisted men: http://www.quarterdeck.org/uniforms/uniforms.htm
Other than the diameter of the crown, the blue cap didn't change much between WW1 and WW2. One change that was made early in WW2 was the elimination of the name of the ship on which the sailor was serving from the cap ribbon. If the sailor served aboard ship and his cap says U.S. Navy, it's a sure bet he served in WW2 or after.
A good site for finding ships' histories is: http://www.hazegray.org/navhist/
Click on the link US Warship Histories - DANFS at the bottom of the page and you will be linked to The Dictionary of American Naval Fighting Ships online - a great source for information on a wide range of naval vessels from all periods.
For technical data on ships, nothing beats Jane's Fighting Ships. Published each year since 1898, these books contain technical data on naval vessels from nations all over the world. Difficult to find (usually found in used bookstores), they are worth the search for the serious study of warships.
To Join the Company of Military Historians click here