Athena: Athena is the goddess who most favours Odysseus in Homer's Iliad and Odyssey. Odysseus' distinguishing characteristic is cleverness, which would have been considered a gift of Athena. She often intervenes on his behalf with the other gods and occasionally forestalls Poseidon's malice. She also, in disguise, acts as a mentor to Telemachus.
Poseidon: Poseidon is angry at Odysseus because Odysseus blinded the Cyclops Polyphemus and serves as the main hindrance and antagonist to Odysseus throughout the story.
This is portrayed explicitly in the first few pages of Book I of the Odyssey:
[I:44] Then the goddess, flashing-eyed Athena, answered him: "Father of us all, thou son of Cronos, high above all lords, aye, verily that man lies low in a destruction that is his due; so, too, may any other also be destroyed who does such deeds. But my heart is torn for wise Odysseus, hapless man, who far from his friends has long been suffering woes in a sea-girt isle, where is the navel of the sea. ... Yet thy heart doth not regard it, Olympian. Did not Odysseus beside the ships of the Argives offer thee sacrifice without stint in the broad land of Troy? Wherefore then didst thou conceive such wrath against him, O Zeus?"
"Nay, it is Poseidon, the earth-enfolder, who is ever filled with stubborn wrath because of the Cyclops, whom Odysseus blinded of his eye."
In some ways it could be argued that the influence of Poseidon, because it forces Odysseus to be clever and resourceful, is in some ways just as positive as that of Athena, even if not so benign.