The Other 00's
Ian Fleming's Moonraker it's made clear that there are three double 0 agents with Bond being the most senior of the three. The others are numbered 008 and 0011.
In the film Thunderball, however we see all 00 agents attending a conference in MI6. There are nine chairs, of which Bond sits on the seventh from the right. That might mean there were nine double 0's at that point. We don't get a closer view on any of the other agents but the man next to Bond, perhaps 006, has a beard (as seen above).
Played by Glyn Baker
Bill Fairbanks, killed by Fransisco Scaramanga in Beirut in 1969 (The Man With The Golden Gun, does not appear).
A later 002 took part in an exercise attack on Gibraltar (The Living Daylights, played by Glyn Baker).
Role Not Credited
Found dead in Siberia, carrying a microchip stolen from a Russian factory. The microchip was found inside a locket which implies that he has a wife and child (A View to a Kill, corpse not credited).
Played by Frederick Warder
Killed by a supposed KGB assasin during the exercise attack on Gibraltar in The Living Daylights.
Played by Sean Bean
Alec Trevelyan, believed killed while on a mission with 007 in the late 80s, later appeared as the head of the Janus Crime Syndicate Organization in 1995's GoldenEye.
Played by an unknown (Role not credited)
M's favorite backup agent doesn't actually appear in any of the films but is mentioned twice. First in Goldfinger as M threatens to replace Bond when he thinks Bond may turn the mission into a personal vendetta. 008 is mentioned in The Living Daylights, when M again threatens to recall 008 from Hong Kong when Bond appears unwilling to fulfill M's orders.
Played by Andy Bradford
In the movie Octopussy, 009 was killed in East Germany by Mischka and Grischka, the knife-throwing twins. 009's spectacular clown-costume entrance to the British Embassy is overshadowed by his death and the much sought-after Fabergé egg he holds as he dies.