Being British and also fantasy, it would make sense that the Harry Potter world would at least pay homage to Middle Earth. J.K. Rowling spent seven years writing the first book in what had to have been a labor of love. Creating a new world, rich characters and a dense history, she received a mere $4,000 advance on the second book. She has since become the first person to make a billion dollars on books. A billion dollars! Her story is always an inspiring one to remember. She didn't set out to make a billion dollars, instead she spent many years working on something than most would have given up on but a love for it drove her to finish.
In the Order of the Phoenix, Voldemort builds up an army and Harry Potter fights for his right to fight - much like the Hobbits in the last Lord of the Rings.

Harry Potter is Frodo - an innocent who bears a burden and is always the target of evil.
Lord Voldemort is Lord Sauron - pure evil, defeated once and gaining the power to reincarnate.
The scar is the ring - the burden becomes more painful as evil is near.
Dumbledore is Gandalf - the wise leader.
Sirius Black is Aragon - the outsider who helps our innocent.
The Deatheaters are Saruman - respected and powerful, they've defected to the dark side.
Malfoy is Gollum - unusually corrupted, he wants what the innocent has.
Wormtail is Grima Wormtongue - witless servant to the dark lord.
The Dementors are The Nazgul - faceless and cloaked in black, they are terrifying creatures.
I know that these parallels are also found in Star Wars and any great epic or adventures with classic heroes and villains from mythology. I still look forward to seeing what's to be found in the fifth Harry Potter.