Frodo, in this manner, is a sort of "Everyman", the quintessential Man, the best, most humble and brave of us, all wrapped up into one person. He makes the journey for us, with help from his companions, who are each brave and decent folk in their own right (though perhaps flawed in some way that Frodo has learned to master). Frodo then becomes an Earendil, a divine messenger for humanity, a representative of Fallen/physical Middle Earth, who is sent by his people to Valinor to beg for their divine aid. Just as Earendil braved almost certain death by daring to sail into the west from which they were banished (cf Banishment from Eden), Frodo must not journey into the far East, into Hell (instead of west, into Heaven). He must now make that journey to destroy the Ring, to destroy Gollum, who represent the worst in Frodo, the worst in mankind, the worst of Melkor, as opposed to what he could have been (Aule).
what is clear, however, is that Gollum HAD to die. Gollum, who represents the physical side, the side that can only be destroyed in the forges from which it was made (i.e. the pits of Hell).
Frodo was eventually let into Valinor/Heaven. (which means he was successful in his endeavor)
Frodo's "throwing of the Ring into the pit of lava" (or, rather, Gollum's biting of Frodo's finger and falling into the lava) is then symbolic of Frodo "killing" off that physical/lustful/carnal side of himself. (for an excellent discussion on what it means to "kill off the physical/carnal side", read Schopenhauer's World as Will and Idea. Destroying the Ring is then a killing of the ego, of yourself, your pride, envy, sex drive, ambition, basically becoming a monk/nun that lives up to the name (not to be confused with the modern day variety that keep ending up in the news over scandals). To be a monk/nun without feeling the need to shout to the world that you're a monk/nun, to do it for yourself and for you alone, or for God, "to pray behind closed doors, and not with loud exclamations in the market place for all to see" (Jesus Christ quote).
To become like Tom Bombadil, basically, unknown to the world, unconcerned with the world and its coming and goings.
Which makes me think Tolkien was into hermetism, or gnosticism, free-masonry, or something like that, because don't the masons have a hand sign they make where it looks like they're missing two fingers from their hand? (they disguise this by putting the "missing" fingers in their coats, and there's also a reference to this whenever Bilbo or Frodo "looks for the Ring" in the pocket.
