It's well known that Jesus was not the first deity said to have been resurrected from the dead. The Egyptian Osiris was killed and brought back. Odin sacrificed himself on the World Tree for wisdom, which wouldn't have done him much good if he hadn't come back to life. Bacchus/Dionysus was resurrected in a rather different manner, with his mother having died and his being born from Zeus's thigh. Another deity I've seen mentioned in this context is the Phrygian Attis, but the evidence for this isn't fully convincing. A quick Internet search has resulted in some usually fairly thorough sources, like Wikipedia not even mentioning resurrection, but merely the preservation of Attis' body. Still, there do seem to be some parallels between the festival of Attis and the celebration of Easter, so it's as good a time as any to discuss this mythical figure.
Attis originated in Asia Minor, although some aspects of his worship later spread to Greece and Rome. His birth story begins with Cybele, the Phrygian Earth Mother goddess. She had as a child a hermaphroditic demon named Agdistis. The Greek version of the story says that Agdistis was conceived when Zeus, having his sexual advances toward Cybele rebuffed, resorted to masturbating on top of her. I'm inclined to believe this wasn't part of the original myth, but rather something added by the Greeks to tie it in with their own pantheon. And since the Greeks already HAD a Mother Earth figure in Gaia, Cybele seems to have been retconned as a more minor nature deity. Anyway, the gods were just as frightened by a double-gendered deity as many people still are today, and castrated the demon. The cast-off genitals grew into an almond tree, and when Nana, the virgin daughter of the river god Sangarius, pressed one of the almonds to her breast, she ended up pregnant. (See, I TOLD you abstinence wasn't an effective way to prevent pregnancy!) Nana left her son Attis out in the wild to die, but he was tended by a goat and later adopted by humans, although their names apparently weren't worth mentioning. Cybele fell in love with the beautiful youth, apparently not knowing he was, in bizarre convoluted fashion, her grandson. When Attis tried to marry the Princess of Pessinus, Cybele became angry at him, and either she herself or Agdistis showed up at the wedding to drive Attis insane. In his madness, he castrated himself, and for some reason his father-in-law (whom some Greeks identified as Midas, the guy who had the golden touch at another point in his life) followed suit. Attis then died, but Cybele managed to preserve the body. At least, that's what appears to have been the more common story, and the one that can be linked with Easter. The Lydian version says that Zeus, jealous of the people's worship of Cybele, sent a boar to kill Attis and other Lydians, which is why the Gauls of Lydia didn't eat pork.
The festival of Attis, which lasted well into Roman times, involved cutting down a pine tree (the kind of tree under which the mythical character died), decorating it with violets (which sprang from Attis' blood as he died), and bringing it to a sanctuary, where the priests would cut themselves and sprinkle their blood all over the tree. These same priests were known to castrate themselves when entering into the order, in veneration of Attis' own actions. If you had a low tolerance for pain, Attis probably was not the god for you. Anyway, the worshippers mourned the dead Attis for three days, after which they had a wild celebration of his resurrection or bodily preservation. By the Roman calendar, this festival took place on the twenty-second through twenty-fifth of March, around the time of the vernal equinox. Although the date of Easter is based on a lunar calendar rather than a solar one, 25 March was often associated with Jesus' death, as well as his conception. There was a belief at that time that his living an exact number of years had to do with his being a prophet, or something like that, although I don't know how that idea originated. I'm sure it was no coincidence that this had him being born at the beginning of winter and dying at its end, nor that it meant Christian holidays could be transplanted onto existing pagan festivals. And the spring death does make sense, as Jesus is said in all known sources to have died during Passover. If Easter was influenced by the festival of Attis, that could explain why it's common rhetoric that Jesus was dead for three days before coming back to life, although the story as told in the Bible makes it only about a day and a half. It's also possible, however, that this figure is to coincide with Jonah's being inside the big fish for "three days and three nights." Or maybe it's both.