There are a confirmed 11 minigames. They are as follows:
STAGE01
Chica's Party
BB's Air Adventure
Happiest Day
Glitch Minigame
Mangle's Quest
Night 1
Night 2
Night 3
Night 4
Night 5


BB's Air Adventure -

How To Enter:
Go to CAM 8 and double click the drawing of Balloon Boy on the top left.
Accessable on all nights.

The Minigame:
You play as Balloon Boy or BB and wander around a small map and collect balloons.
There is another balloon above the map to show score with an Eight next to it that goes down.
Once the seven on the map you start on, a door with the word "EXIT"  appears, and if you touch it
you go back to the night you were on. If not, on the very to left, you see wall. But it isn't there.
A secret door lies hidden there. If you enter it, you fall through a gray static
 down to another level with a  barren blue-striped landscape with a tree-looking silhouette
with three crying silouetted BBs. Sometimes, when you fall, you come to a line of floating
balloons with flat tops. You jump from balloon to balloon and find a blue platform
that goes about half-way across the screen horizontally. At the end of it, there is a dead
lifeless gray child.

Mangle's Quest -

How to Enter:
If you go on CAM 7 and look at the arcade machine,
you will notice buttons on said arcade machine. On the
left side of the machine, there are 4 buttons.
Click first the top left, then botton left, then top right, then bottom right.
Only available on NIGHT 2!

The Minigame:
Going through a building (as seen in above picture) at night ( look at the window)
Collecting her endoskeleton and other animatronic parts (starting as a head),
she comes upon a frightened boy (also seen in picture). If this boy is touched the minigame
ends. Once all of her pieces are collected, a door appears and you are allowed to leave.

Chica's Party

How to Enter:
You may notice, (On night 3) Cupcakes strewn about in
the various cameras. If you click all 4, you begin Chica's Party.
Only accessable on Night 3.

The Minigame:
You gather cupcakes and give them to crying children.
Upon recieving a cupcake, they spring up with joy.
There is an area below the pictured area, with two more cupcakes and children
to make a totale of 4 cupcakes and 4 children.

STAGE01

Entering the Minigame:
Inbetween the trash can and the toy box, there is a 3x3 space
of tiles. Think of it as a number pad like you might see on a
calculator, the top being 1-2-3, middle 5-6-7, bottom 7-8-9.
Type this code in (As found in a end-of-night minigame):
395248
Once this has been typed in, you enter the minigame.

You control Golden Freddy on a stage with a un-damaged springtrap, bouncing as if in a show.
3 children are watching with their hands up and bouncing. If you can get out of this room (by going into the crowd and
then straight back at the stage without jumping), there are 9 duplicates that you can find with black all around, one that only
has two children (the rest having 3).


End-Of-Night Minigames:
If you look at the picture at the very top you can get an idea of
what it is like.


One by one you play, in three separate mini games,
as first Freddy, then Bonnie, then Chica, then Foxy.
You are controlling them through a seemingly abandoned
Fazbear's Pizza. Clues to it being abandoned include: Rats,
Puddles of a mysterious black fluid, leaking roof, and other puddles of lighter grayish fluid.
Once you leave the stage (using W, A, S, D controls) you can see a gray and black
Tiled pizzeria with many halls- not like any of the game's pizzerias.
Upon going through one of these halls a code appeared on the side of the passage-
395248. This code can be used to enter the Stage minigame. (see below)
You can also find piles of parts on a big table in a seperate room.
If you go to the right, Purple Freddy will appear (standing) and
a message appears that says "Follow". If you do as it says,
you come into an empty room with a boarded up metal door.
Purple Freddy continues upwards through a passage, and if you try
to follow, "ERR" appears in red, meaning (I assume) "Error".
Upon this discovery, the purple man runs out and disassembles you.
He comes from the area Purple Freddy disappeared to in the first 2
Mini games on night 1 and 2, then on the 3rd, he comes though the
boarded door, and it, all the while, stays boarded up in the same way.

Characters in these minigames: