Prisoners, also starring Jake Gyllenhaal, directed by Denis Villeneuve.

Red Riding: In the Year of Our Lord 1974

http://www.imdb.com/board/11259574/?ref_=nv_sr_2
Red Riding: In the Year of Our Lord 1980

http://www.imdb.com/board/11260581/?ref_=nv_sr_5
Red Riding: In the Year of Our Lord 1983

http://www.imdb.com/board/11259573/?ref_=nv_sr_3

jfk. JFK still has some unsubstantiated evidence just like the zodiac, but alot of it is accurate. Go see it, one of the best 90's movies

Two excellent late sixties British psycho-thrillers that start as police procedurals but get progressively darker are Freddie Francis' 'The Psychopath' (1966), from a script by Robert Bloch, and Gordon Hessler's 'Scream and Scream Again' (1969).

The only movie similar to this is Memories of Murder and imo Fincher plagiarized that movie. Its also much superior to Zodiac.
look above.

As someone already posted, The Town that Dreaded Sundown.

One movie that caught me by surprise recently on Netflix was "The Arrival" (1996) with Charlie Sheen. While Sheen isn't everybody's cup of tea, particularly his film comedies for me, this movie's narrative flows rather well and deals with the hyper-paranoia exhibited by those obsessed with Alien/Greys subverting human existence. The big difference may be the reliance on special effects and violent action scenes which is expected in this genre.

Silence of the Lambs, but of course everyone has already seen that movie.
For a bit of old school classic watch Hitchcock's Rear Window

• L.A. Confidential (1997).
• Se7en (another David Fincher film) (1995).
• Copycat (1995) - not a GREAT film, but it is about a fictional serial killer who "copycats" other famous serials. Stars Holly Hunter, Sigourney Weaver, and Dermont Mulroney, who was in Zodiac (2007). It too was filmed in San Francisco, as Zodiac was.
• Dirty Harry (inspired by Zodiac, and featured in the film) (1971).

I'd suggest some more films about real murders such as the great '10 Rillington Place' and 'The Black Pantha'.
For fictional crimes (but with a real-life crime int he background) I'd suggest the three part series 'Red Riding'.
If you liked this you may also like classic films noir such as 'The Maltese Falcon', 'Double Indemnity', 'DOA' or 'The Blue Dahlia' to name a few.

As others have mentioned, I think tonally and structurally, the closest movie to Zodiac is All the President's Men.
By the way, Mr Wenders, I loved Wings of Desire.
Never defend crap with 'It's just a movie'
http://www.youtube.com/user/BigGreenProds

Didn't go through all the posts to see if anyone mentioned it, but Memories of Murder is one that comes to mind. It's a Korean film which I thought was similar to Zodiac.
"You're close, but the sky's closer"

Apologies if it's been named above but (with an outstanding Stephen Rea) is a similar and earlier film about a (real) Russian serial killing. I preferred it to Zodiac and bizarrely it never got a cinema release despite actors like Donald Sutherland and Max von Sydow.
http://www.imdb.com/board/10112681/?ref_=nm_flmg_act_74

The Avengers

Prisoners
http://www.imdb.com/board/11392214/

There is also this Korean film called Mother directed by the same directors of Memories of Murder. It's almost equally as good as Memories of Murder and it certainly has that crime thriller-mystery vibe.

Wow, brilliant article. Thanks for posting!

I agree! I noticed especially that the zodiac killer was played by several different actors in the film, as was "the killer," whoever or whatever that may be, in Cruising.
Most critics completely missed the point of Cruising.
For some thoughtful analysis of this film,
http://www.rouge.com.au/3/friedkin.html
and also another article I read called "The Sound of Violence."

This may seem like a strange choice, but I highly recommend the film
Cruising
for a similar feeling, as well as a psychological portrait of the way a series of unsolved murders slowly change the detective investigating them. It's late 70s Manhattan (even if it was released in 1980), but has a similar dark, period feel, a shifting kaleidoscope of suspects, as well as mounting, unresolved tension and mystery. Two of the few films that have truly given me the creeps. And it takes a LOT to do so, unfortunately.
I was reminded of
Cruising
just now when I was reading this description of
Zodiac
on the WordPress blog Weminoredinfilm.com:
Its a film about the spellbinding, haunting aspects of an unsolved crime, but is not about the crime itself. Its a film about characters who venture down a rabbit hole, chasing an elusive monster in the dark, and the tolls such a pursuit takes. For a film about obsession, its as much a film about what happens to the obsessed when their drives go unsatisfied.
I would apply this same description to
Cruising
without changing a word.

This message has been deleted.

The Game
Black Swan
Silence of the Lambs
Prisoners

How about:
The Maltese Falcon
The Third Man
High and Low
Double Indemnity
The Killing
and
Brick
All of these are somewhat methodical, murder mystery, whodunit types.

This message has been deleted.

Citizen X is similar and very good.
-All those moments will be lost in time, like tears in rain.-