Twilight Sparkle, a ward of the crown ever since she accidentally turned her parents into plants, is dispatched by Queen Celestia to the small hamlet of Ponyville; the Unicorn has expressed fear that an eldritch Alicorn of the past will arise there. And when Twilight Sparkle fails to defeat the fiendish NightMare Moon in the two Queens' former palace of Concordia Arbos, the planet is plunged into night on one side and day on the other. With only shards of rock to her name and a band of ponies at her side, she sallies forth to bring back the Sun. She will traverse field and mountain, desert and labyrinth if she needs to. Will she be able to solve the mystery of the Elements of Harmony? Who was NightMare Moon, and what evils come to Equestria apart from her everlasting night? And why does Queen Celestia believe that making friends takes priority over everything else for Twilight...?

Can be found on TV Tropes.
Has a YouTube reading by our own Alchemystudent.

The Elements of Friendship, Book I: Harmony
The Elements of Friendship, Book IS [interlude one-point-five]: Bonds
The Elements of Friendship, Book II: Chaoskampf
The Elements of Friendship, Book IIS [interlude two-point-five]
The Elements of Friendship, Book III
The Elements of Friendship, Book IIIS [interlude three-point-five]
The Elements of Friendship, Book IIII

One day, Fluttershy wakes up only to find herself in a changed world. Ponyville and Equestria are not how she remembers them: airships cross the sky, steam-powered machinery drives the economy and the rule of Celestia is no more. In this strange alternate world, Fluttershy reunites with her dear friends and learns of the event that changed history itself. Worse, the timid pegasus seems to have arrived just in time to witness the rapidly approaching climax of a civil war that has been raging for three hundred years...

Pandinus Imperator (You can call him Pan, he won't mind) is knocked back in time during the Canterlot Invasion, and accidentally kills King Sombra on arrival. Instead of being executed, the changeling is surprised to find himself being hailed as a hero, and is promptly put on the throne as the new monarch, the Crystal Emperor. However, Pan now faces a great many problems, among them Celestia and Luna, who seem certain that the changeling is secretly up to no good, as well as several political factions secretly plotting to undermine his reign. There's also the tiny problem of the constant snowstorm that threatens to cut the city off from the outside world permanently.
The Crystal Ponies need a hero now more than ever before. Why did they get a changeling instead?

We Has A TvTropes.

While not truly a part of Bucking Nonsense's Changeling-Verse, the same rules regarding changeling abilities and society apply.

Cover image provided by gabapple, used with permission.

Twilight Sparkle, Sunset Shimmer, and Moondancer are the top students in Celestia's School For Gifted Unicorns. One is a dedicated bookworm with a love of learning, other is an outcast full of ambition, while the last one just wants to enjoy life... a lot.

Connected with unlikely friendship, together, they fight crime live their lives, one day at a time.

(Sometimes they fight crime, too)

While it is set in Stallionverse, knowledge of previous stories is not required (you'll miss a joke or two at worst).

Teen rating and sex tag for slightly edgier humor, innuendos and Moondancer.

Guest chapters provided by the ever talented Eyeswirl the Weirded. You can't hug him through internet (you can try), so give him love by checking his stuff- quality guaranteed.
My own chapters are edited by the ever kind and generous Docontra, whose patience knows no bounds.

Be Awed and Amazed by the tale of Sweetie Belle as she traverses the multiverse in search of her lost mentor and friend, Twilight Sparkle! Will she find her in post-apocalyptic Equestria? Or maybe in a strange world where everypony is the wrong gender? Or even where a Pony claims to be a human? Read as she journeys through very familiar worlds you might have read about... if you dare!

At this point in time all the main worlds to be visited have already been chosen. Thank you all for the suggestions, and I hope you enjoy the surprises!

Here's the official TSC:F Music Intro: The Sweetie Chronicles: Fragments

WDTP: S2/3-CE
You can also visit the TV Tropes Page which has spoilers!

Talks broke down. The unification failed. Hearth's Warming have never occurred. The Great Pony War divided the land, and fears of a prophecy forced the unicorns deep underground and into near extinction.

Almost one thousand years have passed. The curious unicorn Sparkle yearns to breach the surface to discover its many wonders and to search for her missing father and brother, both of whom crossed over many years ago. She is forbidden to leave the safety of her subterranean village of Unicornia until she discovers an orange earth pony washed up on the shores of an underground river. That pony bears one of the six Elements fabled to change the world.

Or destroy it.

Cover art credit goes to ouyrof.

Re:Harmony was conceived before Season 4 aired, so some personalities and character relations do not line up with the show's canon.

Also, please refrain from revealing spoilers in the comments. Thanks!