Twilight Sparkle is called to Canterlot Castle where something has happened to Princess Luna that has reverted her to a weakened state, she has to live with Twilight whilst she recuperates her magic.

This story is a sequel to Oldnew Luna

Twilight and Luna have now been living together for two years. Luna regains her powers over the night sky and the pair must move to Canterlot for Luna to once more take up her duties.

Twilight and Fluttershy go hiking and get all hot and bothered. Typical trashy shipping stuff goes down. All their friends start coming out as well. Also Celestia nearly dies.

There we go.
I hope that appeases the manchildren that didn't like the previous story description.
Feel free to complain in the comments about how a romance story about horses from a show for children has somehow offended your conservative sensibilities.

I'm going to make a delicious sandwich out of black forest ham.

[Featured on EQD 21/4/2014] [Now on TVTropes]

When Luna gifts Twilight the town of Ponyville and its surrounding countryside as her demesne she's initially confused. Then, after double checking her dictionary, more than a little concerned.

All her friends are, legally, her possessions. The town that took her in is her plaything, if she so wishes. She has been given responsibility.

Can Twilight's vision for a modern renaissance outrun the harsh realities of the shadowy figures pulling strings behind the scenes, nobles jockeying for her attention, and an irritatingly metaphorical love triangle?

Special thanks to the insatiable Blue_Paladin42, the incorrigible Maskedferret, the intuitive Southpaw and the indestructible newbiedoodle for all their hard work, past, present and future.

Twilight and Applejack have just discovered their feelings for each other, and all is well until their budding romance is interrupted by an urgent missive from Princess Celestia. Now, Twilight finds herself at a crossroads. Will she leave Ponyville and achieve all that she once desired, or will she decide that she has all she needs on an apple farm in Ponyville?

Meanwhile, Fluttershy and Rainbow Dash are faced with their own choices. Are they just friends, or could they be something more?

This is the sequel to Three's A Crowd. Reading that story isn't required, but it'll give you some additional background.

This story is a sequel to Home Is Where the Hearts Are

In which Rainbow Dash gets in some number of minor quarrels (or "spats"), learns several new words, and gets hit in the face. Also somepony catches on fire, a train never seems to reach its destination, and Fluttershy is largely unaffected by the night's proceedings.

Features RD/PP/FS, R/AJ, and TS/Colgate, so turn back if you find any of that anathematic. Acknowledges that mutually consenting adults in committed romantic relationships may sometimes have sex with one another, but nothing graphic.

Twilight Sparkle wakes from a coma after being cursed by a stallion she doesn't remember ever meeting. Princess Celestia and Spike have been taking care of her while she was sleeping. But something is wrong, and Twilight’s memories don’t match up with anypony else's.

This is an AU story of my own twisted imagination. Set after “Games Ponies Play” but before “Magical Mystery Cure” timeline wise (sort of, you'll see). So no Alicorn Twilight here. Tagged Twilight and Celestia as they are the main characters, but other characters do appear in the story.

Descriptions are hard. Big thanks to my Pre-Readers Nakrab and Dumbgamer99!

-- Soft Story

It's been a week since Twilight became an alicorn and a princess. While walking around Ponyville, she meets each of her best friends, but they didn't act like usual. Twilight tries to figure out what is the reason behind it, she wasn't prepared for the answer she got. How did this happen? Which would be the best way to deal with this problem?

This story is a sequel to Dreams and Disasters

Rainbow Dash has a new problem.

It isn’t that her relationship with Twilight Sparkle has diminished in the year that they have been together, even despite Twilight’s new position as an Equestrian Princess. If anything, the past year has brought them closer together than before. As far as Rainbow Dash is concerned, her life is pretty much perfect. That is, until she notices that her colors are fading.

In a panic to discover what is happening to her, she stumbles headfirst into an ancient secret dating back to long before the formation of Equestria, with her family in the middle. With Twilight and her friends, both old and new, at her side, she will once again venture out into the wide world of Equus, not for love, but for answers. About her family, her heritage, and the theft of the oldest artifact known to pony kind: The Celestial Prism.

Takes place canonically shortly after the Season 3 finale and well before the Season 4 Premier

This story is a sequel to Vanilla Twilight

Rainbow Dash has a problem.

She might be in love with Twilight Sparkle and has yet to admit it to anypony, least of all Twilight herself. After the events of Vanilla Twilight, the two have grown much closer together, spending more time together and sharing their interests. Unfortunately for Dash, Twilight hasn't caught on to her feelings yet, and she could be content with just letting things progress as they are...

If only she hadn't sent that blasted letter admitting it.

Now, thanks to a pair of meddling princesses, Rainbow Dash finds herself on a globe-trotting journey with the subject of her affections. On the surface, it might just seem like a simple task for the Princess, but for Rainbow Dash, it might be the very thing that forces her to come clean with her feelings, or forever face her doubts. For her, in the world of life and love, sometimes it's best to take it one dream and disaster at a time.