Whenever I ask a friend about the symbolism of the Raven from The Raven, they always seem to say death.
Is that the only thing the Raven is meant to symbolize?
I don't believe the Raven symbolizes death at all, but rather life, in grief of having to live after a loved one is dead. As Poe himself put it in his essay Philosophy of Composition:
The reader begins now to regard the Raven as emblematical — but it is not until the very last line of the very last stanza, that the intention of making him emblematical of Mournful and Never-ending Remembrance is permitted distinctly to be seen
Of course authorial intent is only one factor to consider in interpreting a work; see this discussion. It does, however, jibe with my own understanding of the poem even before I read Poe's explicit thoughts on it.
The Raven is thus even sadder than death itself. The speaker craves forgetfulness, and will never have it: his heart shall be "lifted -- Nevermore". He could be content, or at least cope, with loneliness. But the Raven is a constant reminder: he lives not just with the loss but the knowledge of the loss.
Obviously the Raven does represent death. Since we know this, I will not touch on it here. However, there are a few possibilities other than that:
The raven in popular culture (described here) can symbolize many things. Ravens have a wide variety of roles in myths and culture; they can symbolize things from death and war to wisdom to creation of the world.
According many analyses I found while searching (including this one and this one), the raven also symbolizes the narrator's inability to do anything about his eventual fate; since the Raven is perpetually saying the same thing ("nevermore"), the narrator knows what the answer will be. So since the raven usually doesn't speak , this is why he chose such a nonsensical animal.
In addition, the raven's perching atop the bust of Pallas might symbolize it's vanquishing of wisdom and justice.
The raven can also symbolize the devil; since the narrator thinks it is from "the Night's Plutonian Shore" and because it is described as a "demon."