When Ben checks into the hotel, he uses the name Dean Moriarty, one of the main characters in Jack Kerouac's novel 'On the Road'.
The final scene set in London was actually shot in England. Alan Dale could not travel to Hawaii to film the scene due to acting commitments pertaining to his West End role in Monty Python's "Spamalot" production, so the crew came to London, as the scene was deemed too important to be cut. While there have been some choicest of scenes shot outside the islands of Hawaii, this is one of the only two scenes in the entire six seasons to have been shot overseas. The rest is in There's No Place Like Home: Part 3 (2008).
The bottle of Scotch that Charles Widmore keeps next to his bedside the same MacCutcheon brand whisky that Widmore had told Desmond was "too good for him to drink." It is also the same brand that Charlie and Hurley use to get Desmond drunk in Flashes Before Your Eyes (2007).
When Alex deactivates the security fence, she uses the combination 1623. 16 and 23 are both part of the shows prominent number sequence 4, 8, 15, 16, 23, and 42.
When Ben is stopped by the doorman at the hotel, he says that he is there to see Mr. and Mrs. Kendrick in 4E - another numeral in the often referenced number sequence 4, 8, 15, 16, 23 and 42.