Here is a list of some of the nicer items that can help out shamans. This section is not a tell all on what equipment to get, but it gives a good guide on what to look for.
Level 1-15
The equipment you are going to get at this level are grays and whites. You go through these level so quickly that any money spent buying equipment at this level is a total waste. Even vendor armor is not worth it. Keep doing quests and use the equipment that drops from mobs.
Level 15-20
Blackened Defias Armor
(http://www.wowhead.com/?item=10399)
the whole set is great for a enhancement shaman. It can be hard for horde shamans to get.
Armor of the Fang
(http://www.wowhead.com/?item=6473)
the whole set is great for restoration and elemental shamans. It can be hard for alliance shamans to get.
Skeletal Club
(http://www.wowhead.com/?item=2256)
A good one handed mace for low levels.
Stinging Viper
(http://www.wowhead.com/?item=6472)
Another solid one handed mace that can be picked up while you level.
Level 20-25
Killmaim
(http://www.wowhead.com/?item=13016)
is a solid two-handed axe for enhancement shamans.
Slaghammer
(http://www.wowhead.com/?item=1976)
a good two-handed mace for enhancement shamans.
Rod of the Sleepwalker
(http://www.wowhead.com/?item=1155)
A good staff for elemental and restoration shamans.
Meteor Shard
(http://www.wowhead.com/?item=6220)
A good dagger weapon for all shamans.
Warsong Boots
(http://www.wowhead.com/?item=16977) Good boots for horde side enhancement shamans.
Silver-Lined Belt
(http://www.wowhead.com/?item=13011)
Belt for elemental and Restoration shamans.
Level 25-30
Enduring Cap
(http://www.wowhead.com/?item=3020)
Great restoration and elemental shaman head piece.
Spirewind Fetter
(http://www.wowhead.com/?item=9406) Great all around chest piece for shamans at this level.
Barbaric Bracers
(http://www.wowhead.com/?item=18948)
Good enhancement shaman bracers.
Burning War Axe
(http://www.wowhead.com/?item=2299)
Good two-handed axe for enhancement shamans.
Cobalt Crusher
(http://www.wowhead.com/?item=7730)
Good two-handed mace for enhancement shamans.
Advisor's Gnarled Staff
(http://www.wowhead.com/?item=19569)
Good staff for restoration or elemental shamans who have been doing Warsong gulch.
Level 30-35
Fiery War Axe
(http://www.wowhead.com/?item=870)
Is a great two-handed axe for enhancement shamans.
Staff of Jordan
(http://www.wowhead.com/?item=873)
Great staff for elemental and restoration shamans.
Wolffear Harness
(http://www.wowhead.com/?item=13110)
Good enhancement shaman chest piece.
Briar Tredders
(http://www.wowhead.com/?item=10582)
Good elemental and restoration shaman shoes.
Level 35-40
Sheepshear Mantle
(http://www.wowhead.com/?item=13115)
Good elemental and restoration shaman shoulder piece.
Basilisk Hide Pants
(http://www.wowhead.com/?item=1718)
Good enhancement shaman pants.
Pendulum of Doom
(http://www.wowhead.com/?item=9425)
Great two-handed axe for enhancement shamans.
Lorekeeper's Staff
(http://www.wowhead.com/?item=19572)
Good staff for elemental and restoration shamans.
Level 40-45
Kang the Decapitator
(http://www.wowhead.com/?item=2291)
Solid two-handed axe for enhancement shaman
The Chief's Enforcer
(http://www.wowhead.com/?item=9477)
Good weapon for all shamans with the stun effect.
Eleven Chain Boots
(http://www.wowhead.com/?item=13125)
Good boots for enhancement shamans.
High Bergg Helm
(http://www.wowhead.com/?item=13128)
Good elemental and restoration shaman helm.
Level 45-50
Stonerender Gauntlet
(http://www.wowhead.com/?item=17007)
Good hand piece for elemental and restoration shamans.
Windforged Leggings
(http://www.wowhead.com/?item=30070)
Good pair of leggings for enhancement shamans
Glowing Brightwood Staff
(http://www.wowhead.com/?item=812)
Good elemental and restoration shaman staff.
Hammer of the Northern Wind
(http://www.wowhead.com/?item=810)
Good hammer for enhancement shamans in their main hand.
Level 50-55
The Nicker
(http://www.wowhead.com/?item=13285#comments)
Good two-handed axe for enhancement shamans.
Amethyst War Staff
(http://www.wowhead.com/?item=20654)
Good staff for elemental and restoration shamans. Hard to get at this level range though
Demonfork
(http://www.wowhead.com/?item=12621)
Good one-handed axe for Enhancement shamans.
Savage Gladiator Chain
(http://www.wowhead.com/?item=11726)
Get the whole set for an enhancement shaman.
Verek's Leash
(http://www.wowhead.com/?item=22242)
Good waist piece for elemental and restoration shamans.
Level 55-60
From level 55+ you should be doing Blackrock Depths, Blackrock Spire, Dire Maul, and Stratholme for decent gear. Stuff that drops here is what you are going to want to equip.
Level 58-70
From this point on you can fight stuff in outlands. Most of the quest blues are better than old world purples. Use the equipment you come across through leveling.
Type Of Equipment
The following is what type of equipment you are going to want depending on your build.
Enhancement
Enhancement shamans are looking for plus to agility, then stamina, and then strength. This is what type of equipment you want at lower levels. Once you get 50+ you are going to want to start looking for equipment that adds to your critical hit chance and your hit chance.
Elemental
Elemental shamans are looking for plus to intelligence, then stamina, and then spirit. This is the type of equipment you want at lower levels. Once you hit 50+ you are going to want to start getting plus to spell damage and plus to spell critical hit. Then you are looking for Mp5 equipment for longer fights.
Restoration
Restoration shamans are looking for plus to intelligence, then stamina, and then spirit. This is the type of equipment you want at lower levels. Once you hit 50+ you are going to want to watch for plus to healing and Mp5 gear. You then want plus to spell critical hits, so you can get that super heal off.
Totems
There are currently 31 different totems in the game. Totems are kind of like extra trinkets that augment shaman abilities. They are gained through raids, quests and two of them can be acquired as PvP rewards. You are almost always going to have to go get these yourself. Only one of the totems can be bought at the auction house and it is seldom sold. The other 19 are all bind on pick up. Here is a link to all 20 totems (http://www.wowhead.com/?items=4.9#0+1-2). When you pick up a totem, it is pretty obvious what any one is used for. Most shaman switch these around depending on the upcoming fight.