I would assume that everyone has seem the original Evil Dead, but at the screening we had twelve people, and five of us had seen the original. FIVE. This seemed low, because it was. So let's assume seven out of twelve people reading this haven't seen it, even though I know more have.
Evil Dead (1981)
Even though personally, I think the second one is better, you should start where it all began. If you enjoyed the new one, don't expect this to be the same ride. While there are similarities, this is campy and kind of humorous at time. This is pretty much the same story as the remake, but thirty years ago. It's on Netflix, so check it out!
Evil Dead II (1987)
I would say this one is much better than the first. This film has a short recap of what happened in the first movie, so if you can't watch the first one, but can watch this one, you should be okay. In case you haven't seen it, I'm not going to spoil anything, but it's kind of what happens after the demons are gone. This one is much more comedic than the first, like slap-stick comedy. There is no real way to explain the third movie without spoiling the ending here...so in the end Ash is sucked into a time portal and sent to medieval times...
Army of Darkness (1992)
This is the third part in the Evil Dead trilogy. The comedy in this is cheesy and campy, but hilarious. I don't think there are really any scary parts at this point, but it's still a great movie. Ash is sent to medieval times, and accidentely unleashes an army of deadites. He teams up with the locals and tries to hold them off! There are a few versions of this film, I would assume the longest one is the best cut, but I really don't have an opinion on it.
Army of Darkness Omnibus Volume 1 (2010)
This collects the first 18 issues of the Army of Darkness comic book based on the original screenplay, and then the first four arcs of the story. If you are an Army of Darkness fan, this is worth every penny.
Army of Darkness Omnibus Volume 2 (2012)
This collection features 8-13 of the original run, and 1-12 of the second run of Army of Darkness comics. It includes Ash VS Classic Monsters and Death of Ash. Definitely worth checking out. 400 pages for under $25? Deal.
Army of Darkness: Ongoing Series
Dynamite Comics also a monthly ongoing Army of Darkness comic that isn't too bad. It focuses of a girl who witnesses her boyfriend be turned into one of the dead. Her and Ash meetup to travel through space and time to kill 'em all. It's weird, but I've liked the first 13 issues so far. Definitely can't take it seriously, but were you planning to?
Marvel Zombies VS Army of Darkness
This is exactly what is sounds like. Zombie versions of famous Marvel characters versus Ash himself. It deals more with the Marvel Zombies that Army of Darkness, but is still a good read if you can find it. Worth reading.
Evil Dead: Hail to the King (2000)
Evil Dead: Hail to the King is a PSX game from 2000. I am leaving it on this list, but it isn't recommended. In fact, it is pretty bad. If you absolutely have to play it, you should be able to find it cheap, but the controls are absolutely horrendous. Other than that, not a bad game.
Evil Dead: Fistful of Boomstick (2003)
This is what I expect from an Evil Dead video game. I don't want survival horror, I want to stab dead things with my chainsaw arm! The game gets a little repetitive, but it is still a decent game for what it is. Should be cheap to get it used. Available on the Xbox and PS2. Bruce Campbell appears as Ash.
Evil Dead: Regeneration (2006)
This would be considered the best Evil Dead game. The story continues where the second film left off, some kids find the tape in the cabin and you can probably guess what happens. Extremely action oriented, stylized finishing moves and so much gore. It feels a little like Devil May Cry. You also get a side-kick in the form of a half dead dwarf. Bruce Campbell returns to to do the voice of Ash. Available on the Xbox and PS2.
Well, there's my list. What else am I missing?