Ability over Appearance: Daniel Craig got a lot of controversy when he was cast as James Bond because he looked very different from the past Bonds, being derisively referred to as "James Blond." This of course all went away once the film came out and he got rave reviews. He may have invoked the trope, since he refused to dye his hair black for the role.
The Cameo: There's a blink-and-you'll-miss-it appearance by rock-star executive Richard Branson: he's one of the people being scanned when Bond goes through Miami Airport security.
A similarly short appearance by VS Angel Alessandra Ambrosio as a sexy tennis player who gives Bond the eyes in Nassau.
One of the poker players is played by Tsai Chin, who played Ling, the Chinese girl Bond beds in the pre-credits sequence of You Only Live Twice.
Dyeing for Your Art: Daniel Craig buffed up and put on 20 lbs of muscle for the role of Bond. In an aversion of the literal meaning of the trope, many critics moaned about Craig's hair being blonde in the film.
Le Chiffre's stockbroker is none other than Duggan (Tom Chadbon).
The warlord that Le Chiffre meets at the beginning would later go on to appear on the seventh season of 24, ironically enough as a prime minister opposing a similar warlord.
Spanish people watching this film could easily recognize the casino director as Jacques Noiret.
Hey, It's That Plane!: The plane that served as the experimental skyliner is now located at Dunsfield Aerodrome, also home of Top Gear. You can frequently catch glimpses of it behind the test track, and Jeremy Clarkson actually tows it during a tractor "drag" race in one episode.
Irony as She Is Cast: As they discuss their cover, Vesper describes herself as coming from a strict Roman Catholic family. Eva Green herself is an atheist, and was raised in an irreligious family.
The Poker Game!
To get this you have to read several of the original novels, especially Goldfinger. Throughout the series there are references to the game at the Casino Royale including the names and positions of the players. The large black gentleman? Mr. Big from Live and Let Die. The touristy woman to Felix's left? In the book Goldfinger, she and her husband ask Bond to investigate Goldfinger's cheating them.
What Could Have Been: Approximately half the male actors in film were rumored as being considered for the role of Bond. Of note, Henry Cavill was the runner-up, but at age 22, was considered too young.