Many of these had me rolling! Thanks!
“Only Frodo Could Go to Mordor.”
“Got Rings?”
“Put the 'Ro” back in ‘Rohan shot first.’"
“Arwen and Strider sittin’ in a tree …”
“Drive-by wraithing”
“The Black Gate Welcomes You.”
“Make Mine Isengard.”
Sorry, folks, I know I’m bumping this from page 3- but this one just came to me!
This one could be accompanied by a rainbow or maybe a pink triangle:
Frodo and Sam, NOT Frodo and Pam!
“I freed what?”
–Balin
bumping this one back up… really want to see some more !
If you can read this - put down the Palantir!
Not a bumper sticker, but I love this.
“I was there at the end of the 3rd Age of Middle Earth, and all I got was this lousy T-shir-- er, I mean, bumper sticker.”
Battle of the Five Armies Veterans agianst Aragorn
Keep Gondor Clean- Throw your trash in Rohan
amarith,
in the south the word yonder is often used to descride location. Ex. “Your cat is over yonder”. It is most often used amoung the older generations thought the younger people will generally know what it means (i am 18 if you need an age reference), especially in a rural area. It is considered a very ‘country’ thing to say. However in the context you saw it in the root comes more from the western part of the counrty, and is used to mean wandering. Louis Lamour used it best to descride his younger days as his yondering days when he traveled around the world and bounced from job to job. (Look in the back of almost any copy of his books to see the short bio with the reference). Hope this had been helpful.
Thanks- Elishann 
First time posting here, but I felt I should bring this bumper sticker up
“Gollum was pushed”
I saw this one on a car the other day, looked it up on the Web, and found that a Wican supply outfit is marketing it on t-shirts and bumper stickers:
“Do not meddle in the affairs of dragons, for you are cruncy and good with ketchup.”
I think most of us are aware of what the word means, it was just used incorrectly here. First, it is a quote and the quote uses “wander.” Second, yonder, to my knowledge, is never a verb.
“Honk if you love Eru.”
“Have you hugged a hobbit today?”
“I’m Pro-Frodo and I vote!”
I saw that same tag on a black motorcyle in Maryland, and the rider was in black from head-to-toe. It rocked! 
I have that sticker on my locker here at work! Right over my Spongmonkey pictures. My co-workers think I’m weird.
How about, “My hobbit beat up your Nazgul.”
I [heart symbol] my Oliphaunt.
For the responsible pet owner:
I [spade symbol] my Oliphaunt.
And just to round things off:
I [club symbol] my Orc.
They’ll get my ring when they pry it from my cold dead severed hand!
Eru, Swords and Guts Three that keep us Free
I picture this as two bumper stickers on the same bumper:
DOMINATE MIDDLE EARTH
Ask me how
CALL 1-800-I- SAURON
First nine callers recieve free gold ring
Elves Live
You Think L.A. Has Smaug Problems?!
What’s a Picnic Without a Few Ents?