You say Ra, I say Re... let's call the whole thing a mess?
It is crucial to understand that the mythology of ancient Egypt was based on a fragmented tribal underpining... the length of the Nile Valley and the diverse settlements along it have the effect, starting even before the pre-Dynastic period, of generating a diverse and sometimes conflicting pantheon of gods and goddesses, who were sometimes merged or redefined over time. Upper and Lower Egypt were at times significantly different religious spheres. Different cults sprang up in various places and merged and divided multiple times. The Pyramid texts, the Book of the Dead, various coffin texts and monument inscriptions don't all agree or resolve into a single organized group of deities...
That said... I've been researching a lot of this lately for another fanfic (yes, I know I'm going overboard on this, deal with it!) and my rapidly growing collection of books about ancient cultures say:
Re was primarily a creator-god and sun-god, worshipped from about 3000BC to about 400AD in various parts of Egypt, including Abydos. Toward Dynasty V, he was combined with Osiris to become the Re-by-day, Osiris-by-night father figure of the rulers of that dynasty, imparting authority by paternity of the line.
Atum was originally an independent entity, a creator god merged rather early with Re.
Osiris, prior to Dynasty V anyway, had a cult exclusively his own. He was a grain-god as well as the god of the underworld. His worship can also be reliably traced back to about 3000BC in various parts of Egypt. According to the geneaology drawn up by the priests at Heliopolis, Osiris was born of Geb and Nut, and he had three younger siblings: his consort Isis, his adversary Seth, and younger sister Nepthys. Osiris was integral to the Egyptian kingship: the pharoahs were the embodiment of Horus while alive, Osiris after death.
Isis is best known for putting Osiris back together again after Seth tricks him into a trap and dismembers him. Isis concieves Horus, the hawk, after the death of Osiris and after she has reanimated him. She is a mother-goddess who protected the kings of Egypt during their childhood, as they are Horus embodied. Her hawk-goddess cult spread across Egypt and beyond (there are frescoes of she and Horus which are done in the same style and with similar iconography to early Mary and Jesus frescoes), but major centers included Giza and Abydos.
Hathor is another mother-goddess and the cow goddess of love sexuality and dance. Her worship was centered in Dendera. Her father is given as the sun god Re, and she is described as the mother of all pharoahs. Over time, she was given as the mother of Horus, then as a protector of him, as well as his consort.
The legend of Hathor being sent to destroy humankind on Re's order is called "the eye of Re", and in it she becomes Sahkmet or Sekmet, the lion-goddess who is embodied by the burning, consuming rays of the midday sun. There are at least two versions of the legend, but both involve Re stopping the destruction by pouring out a mixture of beer and pomegranite juice upon the delta. In one version, she thinks this red liquid is humanity's blood and becomes horrified with her actions, the other version has her drinking it until she passes out from her own bloodthirsty and drunken behavior. In both she reverts from Sekmet to Hathor afterwards.
From the Book of the Dead (I'm using the Faulkner version, since Daniel Jackson's comment in the Stargate movie that the blackboard translation using Budge's books was so wrong...):
Apep is given as the serpent-demon, arch-enemy of Re.
Seth, god of storms and the desert, is the brother and murderer of Osiris, the rival of Horus, and the guardian of Re against Apep.
The Sacred Eye of Horus was torn out by Seth, and restored by Thoth, and is symbolic of everything good.
Thoth is the moon god of wisdom and learning, and scribe to the gods listed in the Heliopolis pantheon, also sometimes attributed as the god who taught man to write heiroglyphics. He is a mediator between Seth and Horus. In some of my references he is given as a son of Re, in others he was born from the head of Seth.
Sokar is the falcon-headed god of the dead according to the Book of the Dead, and is often combined with Ptah, the creator-god of Memphis.
Qebehsenuef is one of the four Sons of Horus, who are often associated with the four compass directions or winds. The other three were Mesti, Hapi, and Tuamutef. After the 18th Dynasty, the heads of the four were carved on each of four canopic jars, vessels used to house particular organs as part of the mummification process.
Sigh.
I've only seen the first season(thank goodness for DVDs!), so I can't really comment on any of the SG-1 representations other than Apothis (who sounds like Apep to me, although there were a lot of serpent-related gods and goddesses at various times), Ra (close enough to Re, right?), and Hathor (who was a pretty clear reference in the show!).
Hope this helps...
-- Adele
