ROTK SPOILERS dont look if you havnt read book
right here we go, this is info from the book, and rumours iv heard from the movie
theoden dies, in the book his horse is shot wth poison dart falls and kills him, p.j wouldnt change that as the poen is great
denethor also dies, sauron decieves him and he cannot handle the fear anguish and grief, he goes mad, and when faramir is bought back, apparently dead its too much he builds a pyre sets it on fire and throws himself on
merry joins the service of theoden and pippin the service of denethor
as pippin is took to gondor because he looked in the palantir and sauron thinks that a hobbit has the ring, (wrong hobbit mate)
saruman will not be killed in scouring of the shire as that is left out as it would be an anti climax after much bigger actions, he is thrown from his balcony, which he is trapped in by ents, anfter gandalf snaps his staff, he is impaled on a spikey wheel thing. after grima has pushed him legolas fires an arrow up in the air, and there is a pause for about 5 seconds, the audience goes "what the hell was that legolas" but then the arrow comes back down and through grima
sam and frodo battle shelob shelob stings frodo and sam thinks he is dead so he takes the ring and sting (the sword) and goes on alone, although orcs find frodos body and carry him off, sam hears them saying that frodo is not dead only paralyzed teporarily, so sam sets on a second mission to retrieve his master.
orcs strip frodo and the mouth of sauron shows gandalf aragorn legolas gimli and every1 who is to claim war on sauron frodos clothes, and they all believe he is indeed dead
eown sneaks onto the battlefield with pippin (theoden forbade them to go) and the witch king confronts then merry stabs it in the knee, and eown swipes off its head, they both fall into darkness, similar to that of frodos in fotr
gollum appears again and tries to take the ring on slopes of mt doom frodo runs to the top, while sam, finally gets to try and kill gollum, he almost succeds and gollun tells sam "we will die when precious is destryed anyway, wel turn to ashes ASHES" so sam leaves him for the sake of pity, sam walks into mt doom stand on a high slop and cannot see frodo, then he sees frodo much closer to the fire, and shouts for him to destry the ring, frodo does an isildur and says no, but gollum comes and attacks frodo for the ring, frodo puts it on and gollum bites off frodos finger with the ring on, and does a dance of joy but falls into the flames, his last words are precioius
aragorm becomes king and marries arwen, eowen marries faramir