Here we have a list of all the Items in Kingdom Hearts we could find and put them in alphabetical order with a description, price and location. Enjoy!

Credit: Deep and FFFreak

 Name Munny  Description  Location
 Antenna  N/A  Piece of evidence to help prove Alice innocent.  Wonderland; Find three big mushrooms in the Lotus Forest, jump on the middle one and head right.
 Blaze Shard
 N/A  Used for item synthesis at the Synthesis Shop in Traverse Town.  Can be attained from the Heartless: Red Nocturne and White Mushroom.
 Bright Shard  N/A  Used for item synthesis at the Synthesis Shop in Traverse Town  Can be attained from the Heartless: Green Requieme and White Mushroom.
 Camping Set  150  Fully restores all of the party's HP and 3 MP of each party member.  Item Shop located in Traverse Town, chests or won in battle.
 Claw Marks  N/A  Piece of evidence to help prove Alice innocent.  Give the yellow flower (near the Lotus Forest entrance) a Potion and you'll grow very big. Jump onto the tree stump and then hit the tree a few times, then take the seed, eat it and you'll grow back to normal size again. Jump onto the two mushrooms to the right and onto the green leaves you just swivelled round by hitting the tree, go towards the Bizarre Room and look out for that little pink evidence box.
 Cloth  N/A  Needed to build the Raft on Destiny Islands.  Climb up the ladders near the waterfall until you get to a doorway in the tree, proceed and on your right should be the cloth hanging up on the wall.
 Coconut  N/A  Used as food supplies for the journey on the Raft to new worlds.  Lock onto a few palm trees on Destiny Islands and slash some combos at it, some coconuts will eventually fall down.
 Cottage  N/A  Fully restores party's HP and MP.  Can be won from enemies, synthesized by using a Blaze Shard (x2) and Bright Shard (x2) and found in chests.
 Defense Up  N/A  Raises Defense by 1.  Can be won from enemies, synthesized by using a Lucid Shard (x5), Lucid Gem (x3), Lucid Crystal (x1) and Mystery Goo (x1) and found in chests.
 Drinking Water  N/A  Supply for the Raft on Destiny Islands.  Can be attained from the Water Fall near Wakka on Destiny Islands.
 Earth Shine  N/A  Summon Simba.  Talk to Leon at the Secret Waterway in Traverse Town and he'll give you the stone.
 Elixir  N/A  Replenishes all HP and MP of one party member.  Can be won from enemies, synthesized by using a Blaze Shard (x2), Frost Shard (x2), Thunder Shard (x2), Mythril Shard (x4) and found in chests.
 Empty Bottle  N/A  Fill it up with water from the waterfall for your journey.  Kairi gives it to you.
 Entry Pass  N/A  Authorization to play in the games at the Olympus Coliseum.  Go to the Olympus Coliseum (best if you go after completing Deep Jungle) and talk to Phil, he thinks you're Hercules and tells you to move the block, Sora tries to move it, but realizes it's too heavy for him. Phil realizes that you're not Herc and insults you (saying that you're no hero), so Sora says he'll prove Phil wrong in the games, but you find out that you need the Entry Pass. To qualify for the games and to obtain the Entry Pass, you need to do the time trial; by smashing barrels in the time limit. After smashing the barrels, Phil still won't give you the Entry Pass, so you storm outside and Hades comes along. After a small chat, he gives you the Entry Pass.
 Ether  100  Replenishes 3 MP of each Party member.  Can be bought from the Item Shop in Traverse Town, won from enemies and found in chests.
 Fish  N/A  Provision for the voyage.  Swim around the sea that surrounds Destiny Islands on the search for small fish. Just simply swim into them.
 Footprints  N/A  Piece of evidence to help prove Alice innocent.  In Lotus Forest explore to your right near two mushrooms to find it.
 Frost Shard  N/A  Used for Item Synthesis at the Synthesis Shop in Traverse Town.  You can win it from Blue Rhapsody and White Mushroom.
 Hero License  N/A  Proves that the bearer's a "Junior Hero".  You acquire this after defeating Cerberus at the Coliseum during the trials.
 Hi-Potion  60  Replenishes 60 HP of one character.  Can be purchased at the Item Shop at Traverse Town, found in chests and won from Heartless.
 Log  N/A  Vital for building the Raft (duh! ^__^).  1st Log: Under the bridge connecting to Riku's favourite spot (the Island he hangs around on). 2nd Log: On Riku's island.
 Lucid Shard  N/A  Used for synthesizing.  Can be attained from the Heartless: Shadow and White Mushroom.
 Mega-Ether  N/A  Restores 3 MP of each of your party members.  Can be found in chests, won in battles and synthesized by using: Blaze Gem (x3), Frost Gem (x3), Thunder Gem (x3), Bright Shard (x5) and Bright Crystal (x1) at the Synthesis Shop in Traverse Town.
 Mega-Potion  N/A  Restores 30 HP of each of your party member.  Can be found in chests, won in battles and synthesized by using: Blaze Gem (x1), Frost Gem (x1), Thunder Gem (x1) and Mythril Shard (x2).
 Megalixir  N/A  Replenishes all of the party's HP and MP.  Can be found in chests, won in battles and synthesized by using: Bright Shard (x5), Bright Gem (x3), Bright Crystal (x1), Shiny Crystal (x1) and Gale (x2).
 Mushroom  N/A  Another supply for the Raft.  The locations of the mushrooms are as follows: At the bottom of the ladder to the left leading to the gliding thing in the second section of the island. Push a small rock aside to find another in a small cave near the raft in the second part. And finally in the secret cave where you find 'the door'.
 Mythril  N/A  Used for item synthesis.  Can be attained from the Heartless: Angel Star and Behemoth.
 Mythril Shard  N/A  Used for item synthesis.  Can be attained from the Heartless: Barrel Spider, Pot Spider and Behemoth.
 Navi-G Piece  N/A  Cid installs it into your Gummi Ship allowing you to go to new worlds.  After defeating Trick Master in Wonderland you get rewarded with a Navi-G Piece. After locking Deep Jungle keyhole you get rewarded with a Navi-G Piece. After sealing the Traverse Town keyhole you get rewarded with yet another Navi-G Piece. After sealing the Neverland keyhole you get yet another Navi-G Piece. And finally there is a hidden Navi-G Piece in the Secret Waterway at Traverse Town.
 Old Book  N/A  Allows you to access the Hundred Acre Wood.  Cid repairs this mysterious book for Merlin, you are then given an errand to take it back to Merlin who lives in the 3rd District of Traverse Town. Once taken back, you can then access the Hundred Acre Wood once opening the book.
 Orichalcum  N/A  Used for item synthesis.  Can be attained from the Heartless: Invisable and Behemoth.
 Postcard  N/A  Slip all 10 Postcards into the red letterbox at Traverse Town and and you'll receive a prize.  Click Here for the whereabouts of the Postcards.
 Potion  25  Replenishes 30 HP of one party member.  Can be bought from the Item Shop in Traverse Town, found in chests and won from battles.
 Power Shard  N/A  Used for item synthesis.  Can be attained from the Heartless: White Mushroom, Bouncywild and Powerwild.
 Pretty Stone  N/A  A pretty stone that's worth very little.  You are rewarded it after you beat Riku in a race on Destiny Islands.
 Rope  N/A  Essential for building the Raft.  In the corner near Tidus up in the Treehouse.
 Seagull Egg  N/A  A provision for the Raft.  At the beginning of the bridge that connects to Riku's Island is a palm tree, on top should be a Seagull Egg. But to get it you need to climb up the palm tree next to it and jump accross to the egg.
 Slides  N/A  6 of Jane's slides that you must retrieve.  The locations are as follows: On top of Jane's tent, big stack of boxes near the globe, on top of the long row of tents to the left of Jane's tent, near the easel, on the green dresser to the left of Jane's tent.
 Spirit Gem  N/A  Used for item synthesis.  Can be attained from the Heartless: Air Soldier and White Mushroom.
 Spirit Shard  N/A  Used for item synthesis.  Can be attained from the Heartless: Soldier, Large Body and White Mushroom.
 Stench  N/A  Piece of evidence to help prove Alice innocent.  Wonderland: On top of the fireplace in the Bizzare Room.
 Thunder Shard  N/A  Used for item synthesis.  Can be attained from the Heartless: Yellow Opera and White Mushroom.