"The Raven," by Edgar Allan Poe, consists of 18 stanzas. Each stanza contains numerous examples of alliteration; that is, of words in close proximity that begin with the same consonant sound.
I will give some examples from the first few stanzas; after that, you should find it quite easy to find more examples on your own.
Stanza 1: once (pronounce "wuns"), weak, weary
Stanza 2: surcease of sorrow
rare and radiant
Stanza 3: filled, fantastic, felt
What is the "action," or purpose, of all this alliteration? Poets use alliteration for a variety of reasons.
Sometimes, they just enjoy the sound.
Other times, alliteration serves to focus the reader's attention on a particular phrase. For example, in the third line of "The Raven," Poe may have wanted to stress the idea that he had been falling asleep before the raven knocked on his door; thus, he used alliteration:
While I nodded, nearly napping...
Occasionally a poet may use alliteration to create an onomatopoetic effect--that is, so the words will sound like the idea or action that they represent. In a translation of Dante's "Inferno," there is a line that reads:
I saw it there, but I saw nothing in it, except the rising of the boiling bubbles.
The repetition of the "b" sound in "boiling bubbles" sounds a little bit like actual boiling water (see link below).