A scene where Paul throws one of the dying rednecks who were trying to kill him in to the cabins previously unseen basement. The original release only had a brief mention at the end by the authorities about "finding a dead body in the basement", with no explanation to the audience about who they were talking about.
Bert's death is shown in explicit detail, namely, his head getting blown to pieces by a shotgun.
A brief extra scene during the night before the final day. In it, we see that Jeff is now sleeping in bed alone and his girlfriend, Marcy, is now sleeping (fully clothed) with Paul. This alludes to a fight between Jeff and Marcy, and also Marcy growing closer with Paul, a plot point that culminates with their sexual affair the following morning.
Cerina Vincent's depressed demeanor during her final scenes (after Jeff breaks up with her) was enhanced by the filming conditions - It was well after midnight for most of those scenes and the set was freezing cold. As if that wasn't enough, you'll remember that poor Cerina was buck naked for most of those scenes. Also, she hadn't even expected to film those scenes on that particular day. Some accidents on set meant that the filming schedule had to be changed on the fly, meaning that Cerina suddenly had to prepare for sex and nude scenes she thought weren't being filmed for some time yet.
The awkwardness during the impromptu sex scene between Cerina and Rider Strong drew from the genuine awkwardness between the two actors at the time - particularly their involuntary bodily responses to the "action". Rider Strong reportedly said to Cerina Vincent, while the scene was being filmed that it was "Very Unsexy." Paul seems to have the exact same sentiments.
Turned Up to Eleven during the bathtub scene, as Cerina Vincent, once again buck naked on a freezing cold set was sitting in a cold bathtub full of goo and fake blood associated with her prosthetic makeup. While completely sanitary, Cerina reveals on the DVD commentary that it felt extremely ickky.
Jordan Ladd's distress during her final "faceless" scene was genuine as she had just moments earlier seen herself with the gruesome mask on in a mirror for the first time and the sight reportedly drove her to tears.
Executive Meddling: Eli Roth had been shopping the script around since the 90s. Once Scream came out, he faced executives trying to make the film more like that.
The Other Darrin: The initial dog hired to play Dr Mombo was too old and tired to perform many of the stunts, giving the filmmakers only about a minute or so of usable footage. With no time to hire a replacement, they used an actual police attack dog. It was so vicious, no actors could appear with it on camera.
Real Life Writes the Plot: Joey Kern suffered from repeated eye injuries during filming and had to get treatment, requiring several scenes to be changed around in the schedule. The leg-shaving scene and Marcy and Paul's sex scene were filmed during the night, using artificial sunlight. This gave the impression that the light levels are darkening as the horror increases.
Similarly Named Works: A lot of people were quick to notice not only how similar The Cabin in the Woods' title and premise (at least what could be gleamed of it during production) was to Cabin Fever, but also how incredibly similar its original pre-release poster was to the Cabin Fever poster. For an added bonus, both movies feature former Power Rangers - Cerina Vincent and Anna Hutchison. Both actresses are playing The Whore, both go topless and both die first. Oh and both were the Yellow Rangers too.
Those Two Actors: Cerina Vincent and Joey Kern, the hot-and-heavy boyfriend/girlfriend duo from this movie reunited a few years later to play husband and wife in a movie called Complacent.
Throw It In!: The infamous "pancakes" scene was thought up because Eli Roth saw Matthew Helms practising tae kwon do between takes.
Too Soon: The audition scene for Marcy was the "it's like being on a plane" duologue just before and Paul have sex. Unfortunately the date schedule for the auditions was September 11th 2001. Despite producers trying to call them off, they went ahead as planned anyway.
Tuckerization: The sheriff 'Frumin' is named after one of Eli Roth's professors in NYU.
Wag the Director: Eli Roth wanted Marcy to be fully nude for her sex scene with Paul. Cerina Vincent however had just come from Not Another Teen Movie where she played the student who never wore clothes. Not wanting to be typecast as a nude scene actress, Cerina refused to show her ass. After much arguing, they came to a compromise - Eli Roth measured one inch of her ass (with a ruler!) that would be visible on camera and taped a Modesty Bedsheet to cover the rest.
Ironically in contrast to the above, Marcy was down in the script to wear a robe for the scene where she sees the hand-prints on her back. Cerina Vincent found the scenario unrealistic and volunteered to go topless for it anyway.
Eli Roth was going to play Winston himself, but Giuseppe Andrews gave a really impressive audition. Eli then took the smaller role of Justin.