Minecraft spawning items with inventories in them

In order to rotate a block, you must specify the Block Data which is essentially its rotation. In terms of the actual command you want created it would look like this, which works as of 1.8.9:

/summon FallingSand ~ ~ ~ {Block:"minecraft:dispenser",Time:1,Data:5}

As you can see the only thing I added was the Data tag and then the direction I wanted. The full list of directions and their values is in the link above, but just to reiterate them:

• 0: Dispenser facing down
• 1: Dispenser facing up
• 2: Dispenser facing north
• 3: Dispenser facing south
• 4: Dispenser facing west
• 5: Dispenser facing east

Your fill statement is almost correct. You have to specify oldBlockHandling, as per the syntax of the command:

fill <x1> <y1> <z1> <x2> <y2> <z2> <TileName> [dataValue] [oldBlockHandling] [dataTag]

(http://minecraft.gamepedia.com/Commands#fill)

Your command would look like this:

/fill ~ ~ ~ ~5 ~ ~5 minecraft:dispenser 0 replace {Items:[{id:"tnt",Count:64b,Slot:0b}, {id:"tnt",Count:64b,Slot:1b}, {id:"tnt",Count:64b,Slot:2b},{id:"tnt",Count:64b,Slot:3b}, {id:"tnt",Count:64b,Slot:4b}, {id:"tnt",Count:64b,Slot:5b}, {id:"tnt",Count:64b,Slot:6b}, {id:"tnt",Count:64b,Slot:7b}, {id:"tnt",Count:64b,Slot:8b}]}

Note that if you want to change the rotation of the dispenser, you would change the dataValue.