Lord of the Rings meets:

by Loanshark
Lord of the Rings meets:

Braveheart:
Frodo: You may take my ring, but you'll never take... MY FREEDOM!!!

Discworld:
Gandalf (riding into Hobbiton on his cart): Aaaaaaaaaaaa.... wizard's staff has a knobontheend, knobontheend, knobontheend...

E.T:
Frodo: Frodo phone home.

Scooby Doo:
Sauron: And I'd have done it too, if it weren't for that pesky Fellowship.

Starship Troopers:
Posters plastered all over Minas Tirith, proclaiming 'A new kind of enemy, a new kind of war.'

Alien:
In Mordor... No one can hear you scream.

Blackadder:
Pippin (approaching the skeleton in Moria): I have a cunning plan...

Charlie's Angels:
Elrond (through old-fashioned looking speaker): Good morning, Fellowship! The Fellowship: Good morning, Elrond!

Silence of the Lambs:
Gollum: It pulsss the ring from itsss fingerses and putsss it in the bassssket.

The Muppet Show:
Aragorn: Ma-nah ma-nah
Boromir: Tu tuuu du du du.

Harry Potter:
Saruman: Okay Gandalf, we'll settle this with a game of Quidditch.

Skippy:
Aragorn: What's that, Skippy? Pippin's pushed a skeleton down the old mineshaft?

Wallace and Gromit:
Gandalf: Cracking cheese, Bilbo!

The Simpsons:
Pippin (after pushing the skeleton in the well): Doh!
Or, alternatively:
Pippin: Mmmmm, second breakfast...

Friends:
Sam (to Frodo): I'll be there for you...

Fawlty Towers:
Gandalf: Don't mention the war!
Sauron: You started it!
Gandalf: No we didn't! You did! You invaded Osgiliath!

The Matrix:
Legolas (sticking an arrow in an orc's eye): Dodge this.

The Terminator:
Gandalf (just before dropping off the brigde of Khazad-Dum): I'll be back.

Star Wars Episode One:
Gollum: Meesa Gollum!

Star Trek:
Gandalf: Keep up, Samwise!
Sam: I cannae go any faster, Gandalf! I'm givin' it all I've got!
Or:
Legolas: He is Aragorn, son of Arathorn. You owe him your allegiance!
Aragorn: ******, Legolas! I'm a doctor, not a king!
Or:
Pippin: Our mission... quest... thing: to boldly go where no hobbit has gone
before.

Grease:
Aragorn & Arwen: You're the one that I want, hoo hoo hoo!

Wayne's World:
Frodo (to Galadriel): If you ask it of me, I will give you the ring... NOT!
Or:
Elrond: You shall be the Fellowship of the Ring.
Fellowship: Aaaah! We're not worthy! We're not worthy!

A Fish Called Wanda:
Nazgul (to Theoden on the Pelennor Fields): Hahahaha! The k-k-k-king is c-c-c-coming to k-k-k-kill me!

Rapunzel:
Gandalf (looking up at Orthanc): Saruman, Saruman, let down your silver hair!

Snow White:
The Fellowship: High ho, high ho, it's off to Mordor we go...

Contributions by other people:

The Princess Bride (supplied by Skybly):
Isildur (to Sauron): Hello. My name is Isildur. You killed my father. Prepare to die!

Star Trek again (supplied by Mindblade):
Galadriel: "You will find your courage. Resistance is futile."

A few by StefBaggins:
Dune:
Frodo: "The Ring is Sauron. Sauron is The Ring."
and
Boromir to Galadriel: "Stay away from me with your Weirding Way."

Will & Grace:
Samwise: "Just Sam!"

ER:
Frodo is pushed into the ER on a gueney by Glorfindel, Merry, and Pippin
Sam: "No! He's been stabbed by a Nazgul Street Gang. You have to save him!"
Elrond: "This hobbit is going to die! Take him to Trauma 2!"
Merry follows Elrond and assorted Elf nurses reciting the stats... "BP 90 over 40, Pulse-Ox..."
Elrond: "Give me 50 cc's of Lidocaine..."

Red Dwarf:
Gandalf, as Holly the computer: "Emergency. Emergency. There is an emergency going on."
Merry: "What is it, Gandalf?"
Gandalf: "The ring must be destroyed."
Frodo: "Smeggin' ring! I'll take the ring to Mordor!"
Pippin: "Yahoo! Wooo! Yeah! That's right! Where's that mouse I was chasing?"

Another Red Dwarf one by myself:
Sam: Mr Frodo doesn't just eat mushrooms! I clearly remember last Friday he ate a piece of lembas. He didn't like it, so we poured mushrooms all over it, and he just yummed it up!

Another Muppet Show one (supplied by arwensreplacement):
Uruk Hai: Sar-u-man!
Assorted Orcs: do do dedoo do

Some additions by Hasty Ent:

Highlander:
Sauron: There can be only one...ring

The Godfather:
"Isildur sleeps with the fishes."

Army of Darkness:
Aragorn:  "Hail to the King, baby."

Clerks:
Merry and Pippin:  "Smokin pipe-weed, smoking pipe-weed, drinkin' pints, drinkin' pints..."

Dead Poets Society:
Gandalf to Frodo and Sam:  "Seize the day. Make your lives extraordinary."

Die Hard:
Saruman to Gandalf at Isengard: "Welcome to the party, pal!"

Spaceballs:
Sauron to Middle Earth: "Now you will see that evil will triumph because good is dumb."