The Harry Ransom Center, part of the University of Texas at Austin, has launched an Edgar Allan Poe digital collection, available at http://www.hrc.utexas.edu/digitalpoe. The site has 4,000 images of more than 200 different materials.
A nav to the right will let you browse the collection by types of content (manuscripts, letters to/from Poe, books owned by, etc.) Or you can do a simple keyword search that can be set to AND or OR and also accepts partial words. A search for raven (what else) found 12 results, including manuscripts, books, and a surprising amount of sheet music.
Search results include the creator, title, format, and date (some are undated.) Click on the title of the item for more information including a description and the id number. Some of the items have interesting images, like a handwritten copy of the last stanza of The Raven — but I wish they had allowed more enlargement; the images aren’t particularly detailed. On the other hand the ability to flip through the search results one after the other is nice.