Aside from the similarities already mentioned, there is one that really jumped out at me when I read HP1. That random centaur, Firenze, who saves Harry in the Forbidden Forest plays exactly Gildor's role. Even the dialogue is similar. Then, you can't destory Sauron without destroying the Ring, in which he put a good chunk of his power; you can't destroy Voldemort without destroying the Horcruxes, which contain his soul. Btw, I heard that some JRRT fan sued Rowling for this one
. And Aragog is an exact copy of Shelob.