The comic counterparts of "24" worked as in-continuity looks at things that happened between the various seasons. Another comic series is set to be released before the next limited season taking place in England.
24: Nightfall chronicles a time before Jack joined CTU.
24: One Shot takes place on Jack's very first day at CTU, about 18 months before the first season.
A video game was released that bridged the 2nd and 3rd seasons, 24: The Game, as well as two comics: 24: Midnight Sun and 24: Stories.
24: Cold Warriors supposedly takes place just prior to the 4th season.
24: Redemption was a made-for-TV movie that bridged seasons 6 and 7.