Frodo, Gandalf, and Aragorn are good and all but I think the true heroes of Lord of the Rings are Bilbo and Samwise.

Bilbo had a small part to play in the main plot of LoTR but it was significant. He is the only person in history to give up the ring after prolonged use. He had it for sixty years and was able to give it to Frodo freely. Consider that Frodo only had it for a few months and wouldn't give it up in the end. While they could have forced it away from him, the fact that he had the willpower to give it up shows how special he was and it was not a coincidence that he was the one to bring the ring out in the open to ignite the events of LoTR.

Sam pretty much kept Frodo alive for the last 2/3 of the story. Frodo would have been killed or turned into a servant of the ring probably in the first half of The Two Towers if it weren't for Sam keeping him going. Sam's love for Frodo is one of the strongest bonds in the entire series (if not the strongest) and without it none of it would been possible. Sam also held the ring for a little while and gave it back to Frodo freely, which is rare though not as significant as Bilbo's 60 years of use.