(NOTE: This thread is for part casual, part legacy graveyard decks. Only the two most popular will be discussed in the initial post.)
In MTG, Graveyard decks are decks that win by utilizing the graveyard, like having no library and the library is in the grave and getting a card to two strategically placed in the grave, saved for a certain time.
The two most played in all formats are Reanimator and Dredge.
DREDGE
I have a soft spot for Dredge, for it is my deck of choice, over Reanimator. The price of Dredge decks range from about $160-$400.
Dredge decks have one goal: Fill the grave with nasty stuff, and bring it all back, tilt sideways and win!! But Dredge can easily be set off course. Any graveyard removal (ex. Leyline of the Void 
) and single card removal (ex. Surgical Extraction 
) can stop Dredge dead in the water.
The most common way for Dredge to win is to fill the grave using the Dredge mechanic (ex. Golgari Thug 
) and when Narcomoeba 
hits the grave from your library, it goes straight to the field. Sac three creatures (usually Narcomoeba ) to flash back Dread Return 
, and as a trigger to sacrificing the creatures, Bridge from Below 
triggers, giving you one Zombie token for each creature sacrificed (to win, you need at least two bridges in your graveyard.) and with the flash back of Dread Return , you bring back Flame-kin Zealot 
, declare battle and swing for at least 21.
To assist with the combo above, newer Dredge decks run the combo of Faithless Looting 
and Lion's Eye Diamond 
. You use a single 
produced by something of a Gemstone Mine 
City of Brass 
caliber. Cast the looting, and then sacrifice the LED ( Lion's Eye Diamond ) for , discarding you hand in the process, and flash back the looting to start dredging.
All (or most) Dredge decks contain:
Bridge from Below
Careful Study 
Breakthrough 
Dread Return
Flame-kin Zealot
City of Brass
Gemstone Mine
Cephalid Coliseum 
Cabal Therapy 
There are different variations of Dredge as well. One version runs at least 1x Flayer of the Hatebound 
. Some run Elesh Norn, Grand Cenobite 
and some run Craterhoof Behemoth 
. There is even a version with Bloodghast 
!
Now, for the Dredge sideboard. The sideboard runs bounce (return to the hand), artifact destruction, enchantment destruction and conditional spells (like Darkblast 
) Use the sideboard to hinder the other player[s] from ruining you strategy.
My Dredge Decklist:
Creature (24)
Enchantment (4)
Sorcery (17)
Land (12)
Artifact (3)
Sideboard (15)
REANIMATOR
Reanimator decks are very precise and to the point. Reanimator decks usually cost around $150-$500 to build.
The goal of reanimator is simple: Get big creatures faster than your opponent that do better things than your opponent's creatures. Reanimator, like Dredge, can be set down the wrong track. But Reanimator can deal with the hate a lot easier like with counterspells, which Dredge lacks.
Reanimator is much simpler to explain than Dredge. Simpily put, discard, reanimate and win!! How you do that is by either discarding (
Careful Study ) a good creature (
Iona, Shield of Emeria 
) or two (
Griselbrand 
), or just bluntly ripping it from your library (
Buried Alive 
,
Entomb 
) and then afterwards bringing it back with "reanimation" (
Exhume 
,
Reanimate 
and
Animate Dead 
). A turn 2
Griselbrand is game for most decks.
A simple
counterspell 
can disrupt the Reanimator win-condition. So to help, a lot of Reanimator decks run the all powerful (and all expensive)
Force of Will 
!!!!! To nip problems in the bud, Reanimator runs
Cabal Therapy . The "Classic Reanimator" deck is not a deck anymore due to the release of
Griselbrand . Since
Griselbrand , Reanimator has been about drawing seven, discarding new, big creatures and bringing them back with newly drawn reanimate spells.
All (or most) Reanimator Decks Run:
Force of Will Entomb Exhume Buried Alive Animate Dead Careful Study Griselbrand Iona, Shield of Emeria There is a Reanimator variation that uses
Recurring Nightmare 
and
Angel of Despair 
to blow up permanents. Another popular card run in Reanimator is
Blazing Archon 
. Makes you un-attackable. The best start for a Reanimator deck is the Premium Deck Series: Graveborn. You get a lot of key components for the deck, all in 'FOIL'.
The Reanimator sideboard runs graveyard hate, but not the typical hate. It runs things like
Surgical Extraction to get rid of, 'ahem', Dredge things. Also, the sideboard runs bounce as well.
Here is an example of a reanimator deck, by edge2522 on tappedout.net. It does not run
Griselbrand .
Land (17)
Instant (15)
Creature (8)
Sorcery (17)
Enchantment (3)
Sideboard (15)
I hope this helped for some questions you had about popular graveyard decks. If I missed something, or I said something wrong, please, tell me, so I can fix that for the future. I hope you enjoy!!
