Arthur
While guarding the Hall of Prophecy for the Order of the Phoenix, Arthur was attacked by Voldemort's snake Nagini; the attack was witnessed by Harry, through his mental connection with the Dark Lord. Critically injured, Arthur was taken to St Mungo's. He survived the attack, but was required to take a Blood-Replenishing Potion at regular intervals. At the suggestion of trainee Healer Augustus Pye, Arthur tried stitches, a Muggle alternative, which Molly did not like. However, the stitches were not effective; Nagini's fangs apparently had a poison that dissolved them. Eventually, an antidote to the poison was found and, he was cured, coming home to find fellow Order members Severus Snape and Sirius Black in the middle of a heated argument. Despite this near death experience.
Bill
During the Battle of the Astronomy Tower, Bill was severely injured by the werewolf Fenrir Greyback. Although he wasn't turned into a werewolf, he did develop some wolfish tendencies such as a liking for very rare steaks.
Bill had a pen-pal at a school in Brazil. When his pen-pal wanted him to go on exchange trip, Bill had to decline because his parents could not afford it. His pen-pal, though, was offended and sent him a cursed hat that made his ears shrivel up.
Fred
Died in the Hogwarts War
George
As a result of an injury from Severus Snape's Sectumsempra during the Battle of the Seven Potters, George is missing his left ear, briefly distinguishing him from his identical twin until Fred's death.
Ron
Was splinched when apparating from The Ministry of Magic where Hermione had to act quickly so they wouldn't be caught leaving. Ron's leg was also injured when Sirius Black attacked him trying to get at Ron's pet rat Scabbars, which was really Peter Petegrew transformed. At one point during this scene, Ron can be heard telling Hermione "They might have to chop it" in an attempt to impress her with his injury or to gain some sympathy from her. He was also hurt when playing chess in the first movie where he was sitting on the knight and it was destroyed by the Queen. He was also poisened by accident. He was saved by Harry.
Ginny
Was at one point, possessed by Tom Riddle in the 2nd book. She also had a broken ankle.