If I remember right, I believe Daniel Garrison Brinton collected a lot of serpent/dragon myths in the late 19th century. Also try:
Ernest Ingersoll, Dragons and Dragon Lore
To sketch an outline of a timeline off the top of my head: In prehistoric art there's a lot of water symbolism which seems to be snake-related, and examples of this are present in the Neolithic art of Old Europe (that is, what archaeologist Marija Gimbutas calls Old Europe--not a reference to Don Rumsfeld's term, LOL!). The earliest known written serpent/dragon myths come from the Middle East c. 3000-2000 BC (notably the Sumerian-Babylonian Tiamat, Apsu, and Kur, as well as Egyptian deities such as Apep, Denwen, and Wadjet). In Western Europe, there is archaeological evidence of serpentine deities at Bronze Age Crete, and we have written myths dating from Homer and Hesiod on, with the German/Norse stuff first being documented by Tacitus but I don't think he includes any serpent/dragon myths, for that you probably have to go to Beowulf and the Norse epics in the Middle Ages. In the east, serpents are known in written Indian texts from about 1200 BC on, and earlier in archaeological art finds, I believe; our earliest copies of Chinese literature come from I believe the Ch'in Dynasty in the 3rd century BC (unfortunately Emperor Shih Huang Ti destroyed most earlier records in the late 200s BC, so IMO we don't have reliable written records on earlier Chinese periods), and again there's probably earlier examples in archaeological art finds; I believe the earliest known Japanese written records are from the 8th century AD. In the Pacific islands there are dragon myths, but I don't know the earliest dates these are attested--written records are probably pretty late there, I imagine most of the evidence is archaeological. In America the Olmecs from perhaps 1200 BC on worshipped a deity who appears to combine features of a jaguar and a serpent, and after that serpent-worship was continuous among the Mayans, Toltecs, and Aztecs, with characteristics that IMO resemble India's Kali cult. The North American Indian tribes also have some serpent/dragon myths, which I believe Brinton collects, that bear some resemblance to European dragon-slayer legends. I think there's some evidence suggesting Indian and Chinese dragon traditions influencing the Olmec/Mayan tradition. To what extent there was interaction between these traditions and others I don't know, but I think it'd be worth looking into.