Oliver Wood has been seen in the first four books, as well as the seventh and final book, though he graduated from Hogwarts at the end of Harry Potter and the Prisoner of Azkaban. Keeper and Captain of the Gryffindor Quidditch team, Oliver has been fondly described as a rather maniacal Quidditch fan. (In fanfiction, he is often referred to as a "Quidditch Nazi", in part because of the long and gruelling practices he seems fond of having.)
In the books, he is described as being "burly."
After graduating from Hogwarts in the summer of 1994, Oliver signed with the Puddlemere United Reserve Team. The last time he has appeared in the books was in Harry Potter and the Goblet of Fire during the Quidditch World Cup.
According to BabyNames.com, Oliver is an English name meaning elf army. It would seem that Oliver has a bit of a whimsical side to him. ;)
In the films, Oliver Wood is portrayed by Sean Biggerstaff, whose accent has caused many fanfiction authors to faint mention that Oliver is from Scotland.
In the Harry Potter and the Sorcerer's Stone film, Oliver attempted to ease Harry's first pre-match jitters by telling him about his first Quidditch match. He said that he took a bludger to the head two minutes into the game and woke up in the Hospital Wing a week later. While it is unlikely that this is book!canon, it's still fun to imagine.