Bernard gives Dolores Alice in Wonderland to read: its most famous adaptation has a blonde girl in a blue dress go on an adventure which changes her.
The arc words, "These violent delights have violent ends" come from Shakespeare's Romeo and Juliet. And as noted within the show, Ford programmed some of the Hosts to make plenty of references to Shakespeare.
One of the first lines of the pilot, is 'Can You Hear Me?', said by a human to a Host. It often happens to be the opening words of another AI when starting conversations with humans on Person of Interest, also created by Jonathan Nolan. Also, the bird that Felix is working on "Contrapasso", is a finch. And as the first season ends with the Hosts awakening and starting their rebellion, the music is a cover version of Radiohead's Exit Music (for a Film), which Person of Interest used at the end of season 3 when Samaritan awakened.
In "The Stray", the woodcutter is shown to have a programmed hobby of woodcarving. Two of the carvings, one of a bear and another of a turtle, have etching of the constellation Orion on them. The bear and the turtle are major symbols in The Dark Tower by Stephen King, where they serve as metaphorical and literal guardians of one of the eponymous Tower's six beams. Considering that one of the show's creators previously worked on trying to get the film adaptation of the series out of Development Hell, it's not a stretch to say the symbolism was deliberate, especially considering how similar Westworld is to The Dark Tower in setting and themes.
Logan is made a major ("or a general, or whatever") with a pin that looks remarkably like the one for the Hand of the King on Game of Thrones, another HBO show.
In the first season finale, Dolores describes to the Man in Black (who is revealed to be William) creatures that once roamed the earth the "size of mountains" who later became "bones and amber", an obvious reference (and threat) about humanity going the way of the dinosaur. The reference to "bones and amber" quite specifically brings to mind another Michael Crichton story about a theme park's attractions going haywire.
In the same episode, the tactical response team makes a sweep through the floors. Hector hides among inactive Hosts, but slowly moves his eyes as they go by, reminiscent of the famous scene with Del Spooner and Sonny in I, Robot.
Dr. Ford at one point quotes his distant colleague Dr. Frankenstein: "One man's life or death were but a small price to pay for the acquirement of the knowledge which I sought; for the dominion I should acquire."
In Season 2, GiancarloEsposito once more plays the head of a huge criminal empire in a semi-rural desert environment, and is even doing Gus Fring's accent during his scenes as the new El Lazo.
James Delos' descent into madness as a malfunctioning Host copy is more than a little similar to that of Pinbacker's own insanity in Sunshine. The actual scene with him and William is shot in a manner reminiscent of the climatic conversation in Event Horizon between Miller & Weir.