SF (canon species only; no humans) Ponies were magically and genetically engineered to be the perfect servitor race. They are powerful, adaptable, intelligent and completely under the control of their creators. A laboratory accident frees one such pony from her mental chains, but how can one mare save herself and the rest of her kind if she doesn't even know she's a slave?
This is not the Equestria you know and these are not your little ponies... not yet, anyway.

Tags: Adventure, Diamond Dogs, Gryphons, NO HUMANS (did I mention that already?)
Other tags: historical, mind control, Clarke's 3rd Law, excessive use of high energy physics, before they were famous.
Detailed review by PaulAsaran.
Cover art by endrome , used with permission.
Russian translation (partial -- 'unofficially' completed in the comments)
A Soot-Covered World, book 1.

Throughout all of history, one concept has kept both the written and spoken word from becoming an unintelligible mess. That concept is that most holy of grounds known by some as "grammar." It sets down rules for language to follow, and keeps it free of distortion.

Yet something is wrong. The rules are failing. And only one pony so much as suspects that something is wrong. Something that goes deeper than a simple appearance of errors. Something that could be an attack on the very root of language itself.

My name is Twilight Sparkle, and 350 years ago, Sweetie Belle and I vanished without a trace.
Now here we are, in the future.
Equestria has become a utopia, with everypony living in peace and harmony.
Everything is perfect. All a pony could ever want, and more.
My name is Twilight Sparkle, and I want to go home.

Editing provided by Stereo_Sub and JustAnotherTimeLord.

Cover art courtesy of Geomancing.

Reading by lieilengi

Spanish translation by Spaniard Kiwi

The royal court of Canterlot welcomes its newest member with open forelegs: the human philosopher Voltaire, from Earth.

On Earth, Voltaire is known as the greatest enemy of tyranny in the history of literature, and a legend in his own mind.

On Equestria, the court betting pool is giving him a week before the Princess banishes him to the Moon.

Note: This story doesn't have sequels per se, but there are a couple of short follow-ups set in the present day ("Parade Coverage" and "Secret Histories"), and a prequel of sorts in "At the Inn of the Prancing Pony".

TV Tropes page.

Twilight isn't having a very good day. An experimental spell blew up in her face, an army of changelings is attacking Canterlot, and she just died. Yet somehow, it looks like it's going to keep going downhill from here.

Given the chance to correct what's gone wrong, Twilight swears she's going to fix all this even if it kills her. Which it will. Frequently.

Cover art by Pixel Prism
Spanish Translation
Series TV Tropes page

Sweetie Belle is compelled to learn magic after Rarity promises to teach her the finer art of dressmaking, but only once the young filly has learned the basics of magic. However, learning magic comes with its own set of complications and bears an unforeseen gift that will change Sweetie Belle's life forever.

Here's a one-shot sequel that takes place four days after Scion of Chaos: An Emerald Treasure

And this is a Multi-chapter sequel that takes place 5 years after the events of SoC and AET: A Heart of Change

Here's a poem that's based around the character Red Timber. (Not necessary to read for the comprehension of the storyline): Red Timber

Special thanks to SameAsUsual for letting me use his art: http://sameasusual.deviantart.com/art/Ultimate-Sweetie-Belle-340226445. And to ShadowBro for adding in the title and cropping the image.

[Featured on EqD and FiM Fiction] Chrysalis is brought to Canterlot to stand trial for her failed invasion. Thinking her fate is sealed, she is determined to be defiant to the very end. Loosely based on March to the Scaffold, the 4th movement of the musical piece Symphonie Fantastique by Hector Berlioz.
All links to the music pieces are in the Author Notes.
Dramatic reading of the entire story by Illya Leonov
Dramatic reading of Chapter 1 by xPsychoShyx
Picture is by Huussii

Big Macintosh goes on strike when he sees he's the one doing all the heavy lifting and harder work at Sweet Apple Acres while his sisters frolic. His idea catches fire throughout Ponyville, and soon every stallion is up in arms! Sexism explodes in the tiny town, it's Stallions on Strike!

[Complete] Celestia awakens to see an empty world, white sandstone stretching the horizon. She wanders the world as she builds it from her imagination, filling it with life, but as time passes, the world that she created begins to seem like little more than a lucid dream, conjured from the dust.

It's Sisterhooves Social time again. This year, Dash catches wind of two new competitors and gets Spike to bet on the race. When her team is revealed to be a rather famous set of siblings, it looks like poor Spike will be her slave for a week! However, due to a team of masseurs, a minor invasion, unfortunate addictions, and dubious barrel components, victory might not be as near as she thinks...