[GS]Item Locations:

TMs / HMs:
TM Number: 01
Move: Dynamic Punch
Location: Cianwood City Gym

TM Number: 02
Move: Headbutt
Location: Goldenrod Department Store / Ilex Forext

TM Number: 03
Move: Curse
Location: Celadon Mansion

TM Number: 04
Move: Rollout
Location: Route 35

TM Number: 05
Move: Roar
Location: Route 32

TM Number: 06
Move: Toxic
Location: Fuchsia City Gym

TM Number: 07
Move: Zap Cannon
Location: Power Plant

TM Number: 08
Move: Rock Smash
Location: Goldenrod Department Store / Route 36

TM Number: 09
Move: Psych Up
Location: Traded Abra

TM Number: 10
Move: Hidden Power
Location: Lake of Rage

TM Number: 11
Move: Sunny Day
Location: Rocket Hideout / Celadon Department Store

TM Number: 12
Move: Sweet Scent
Location: Ilex Forest

TM Number: 13
Move: Snore
Location: Blackthorn City Dark Cave / Moo Moo Farm

TM Number: 14
Move: Blizzard
Location: Goldenrod Game Corner

TM Number: 15
Move: Hyper Beam
Location: Celadon Game Corner

TM Number: 16
Move: Icy Wind
Location: Mahogany City Gym

TM Number: 17
Move: Protect
Location: Celadon Department Store

TM Number: 18
Move: Rain Dance
Location: Slowpoke Well

TM Number: 19
Move: Giga Drain
Location: Celadon City Gym

TM Number: 20
Move: Endure
Location: Burned Tower

TM Number: 21
Move: Frustration
Location: Goldenrod Department Store

TM Number: 22
Move: Solarbeam
Location: Route 27

TM Number: 23
Move: Iron Tail
Location: Olivine Gym

TM Number: 24
Move: Dragonbreath
Location: Dragon's Den

TM Number: 25
Move: Thunder
Location: Goldenrod Game Corner

TM Number: 26
Move: Earthquake
Location: Victory Road

TM Number: 27
Move: Return
Location: Goldenrod Department Store

TM Number: 28
Move: Dig
Location: National Park

TM Number: 29
Move: Psychic
Location: Celadon Game Corner / Saffron City

TM Number: 30
Move: Shadow Ball
Location: Ecruteak City Gym

TM Number: 31
Move: Mud-Slap
Location: Violet City Gym

TM Number: 32
Move: Double Team
Location: Celadon game Corner

TM Number: 33
Move: Ice Punch
Location: Goldenrod Department Store / Traded Krabby / Staryu

TM Number: 34
Move: Swagger
Location: Lighthouse

TM Number: 35
Move: Sleeptalk
Location: Goldenrod Department Store Basement

TM Number: 36
Move: Sludge Bomb
Location: Route 43

TM Number: 37
Move: Sandstorm
Location: Celadon Department Store / Tohjo Falls

TM Number: 38
Move: Fire Blast
Location: Goldenrod Game Corner

TM Number: 39
Move: Swift
Location: Union Cave

TM Number: 40
Move: Defense Curl
Location: Mt. Mortar

TM Number: 41
Move: Thunderpunch
Location: Goldenrod Department Store

TM Number: 42
Move: Dream Eater
Location: Viridian City

TM Number: 43
Move: Detect
Location: Lake of Rage / Traded Nidoran M / Nidoran F

TM Number: 44
Move: Rest
Location: Ice Path

TM Number: 45
Move: Attract
Location: Goldenrod City Gym

TM Number: 46
Move: Thief
Location: Rocket Hideout

TM Number: 47
Move: Steel Wing
Location: Route 28

TM Number: 48
Move: Fire Punch
Location: Goldenrod Department Store

TM Number: 49
Move: Fury Cutter
Location: Azalea Town Gym

TM Number: 50
Move: Nightmare
Location: Route 31

HM Number: 01
Move: Cut
Location: Ilex Forest

HM Number: 02
Move: Fly
Location: Cianwood City

HM Number: 03
Move: Surf
Location: Ecruteak City

HM Number: 04
Move: Strength
Location: Olivine City

HM Number: 05
Move: Flash
Location: Sprout Tower

HM Number: 06
Move: Whirlpool
Location: Rocket Hideout

HM Number: 07
Move: Waterfall
Location: Ice Path
Misc. Items
Item: Amulet Coin
Location: Underground Passage

Item: Basement Key
Location: Goldenrod City

Item: Berry Juice
Location: Attach a Berry to Shuckle

Item: Berserk Gene
Location: Cerulean City

Item: Bicycle
Location: Goldenrod City

Item: Black Belt
Location: Lake of Rage

Item: Blackglasses
Location: Blackthorn City Dark Cave

Item: Bright Powder
Location: Traded Articuno / Mewtwo / Moltres / Zapdos

Item: Card Key
Location: Underground Passage

Item: Charcoal
Location: Azalea Town

Item: Cleanse Tag
Location: Route 5

Item: Coin Case
Location: Underground Passage

Item: Dragon Fang
Location: Dragon's Den

Item: Dragon Scale
Location: Mt. Mortar / Wild Dratini / Dragonair / Horsea / seadra

Item: Everstone
Location: Prof. Elm / Route 25 / Wild Geodude / Graveler

Item: Exp. Share
Location: Radio Tower Prize / Route 30

Item: Expn. Card
Location: Lavender Town

Item: Focus Band
Location: Saffron City

Item: Gold Leaf
Location: Traded Dewgong / Hypno / Marowak / Muk / Parasect / Primeape / Raichu / Rhydon / Seadra / Slowbro / Venomoth

Item: Hard Stone
Location: Route 36

Item: Itemfinder
Location: Ecruteak City

Item: King's Rock
Location: Slowpoke Well / Wild Poliwhirl / Slowpoke / Slowbro

Item: Leftovers
Location: Celadon City / Wild & Traded Snorlax / Traded Clefable

Item: Lightbulb
Location: Traded Pikachu (from Yellow only)

Item: Lost Item
Location: vermillion City

Item: Lucky Egg
Location: wild Chansey

Item: Lucky Punch
Location: Mystery Gift / Traded Chansey

Item: Machine Part
Location: Cerulean City 

Item: Magnet
Location: Route 37

Item: Magnifier
Location: Mystery Gift

Item: Map Card
Location: Cherrygrove City

Item: Metal Coat
Location: SS. Aqua / Wild Magnemite

Item: Metal Powder
Location: Traded Ditto

Item: Miracle Seed
Location: Route 32

Item: Moon Stone
Location: Mom / Mt. Moon / Route 27 / Wild Clefairy

Item: Mystery Egg
Location: Route 30

Item: Mystic Water
Location: Cherrygrove City

Item: Nevermeltice
Location: Ice Path

Item: Old Rod
Location: Route 32

Item: Pass
Location: Saffron City

Item: Pink Bow
Location: Radio Tower / Route 29

Item: Poison Barb
Location: Route 32 / Wild Beedrill

Item: Polkadot Bow
Location: Traded Jigglypuff / 

Item: Quick Claw
Location: National Park / Wild Sneasel

Item: Radio Card
Location: Goldenrod City Radio Tower

Item: Rainbow Wing
Location: Goldenrod City (Gold) / Pewter City (Silver)

Item: Red Scale
Location: Lake of Rage

Item: S.S. Ticket
Location: Professor Elm

Item: Sacred Ash
Location: Wild Ho-oh

Item: Secretpotion
Location: Cianwood City

Item: Sharp Beak
Location: Route 40 / Wild Dodrio / Fearow

Item: Silver Leaf
Location: Traded Electrode / Magneton / Rapidash / Seaking / Tentacruel / Weezing

Item: Silver Wing
Location: Goldenrod City (Silver) / Pewter City (Gold)

Item: Silverpowder
Location: Wild Butterfree

Item: Slowpoketail
Location: Mahogany Town

Item: Smoke Ball
Location: Underground Passage

Item: Soft Sand
Location: Route 34

Item: Spell Tag
Location: Blackthorn City / Wild Misdreavus

Item: Squirtbottle
Location: Goldenrod City

Item: Stick 
Location: Wild Farfetch'D

Item: Sun Stone
Location: National Park Contest

Item: Super Rod
Location: Route 12

Item: Thick Club
Location: Wild Cubone / Marowak

Item: Twisted Spoon
Location: Traded Kadabra (from Yellow only)

Item: Up-Grade
Location: Saffron City
By "traded" I mean traded from the previous Pokemon games (RBY).

Thanks have a nice day ^^.
Made a couple of edits as some of the TMs can also be obtained as held items from different Pokemon that are transferred from RBY. I've made sure to note the version exclusives (e.g. Pikachu from the Yellow version to get Lightbulb).

This list is now complete. Thanks have a nice day ^^.