To the folks of ancient Athens, Theseus was the absolute man. They thought of him as the great king who brought law and order to Athens and Attica, the region that surrounded the famous city-state. He was the guy who overturned all the wild and wooly ways of the past and helped pave the way for civilization. He's also credited with spreading the influence and power of Athens throughout Greece.
Tales of his daring adventures were popular subjects of sculpture, pottery, and other art forms, and the myths surrounding him were the subject of many ancient writers. Plutarch, Apollodorus, Hyginius, Didorus Siculus, and lots of other dudes with crazy names all took a shot at chronicling the legendary life of Theseus. The Athenian hero also pops up as a character in some of the great tragedies such as Hippolytus by Euripides and Oedipus at Colonus by Sophocles. Like a whole lot of other Greek myths, the tale of Theseus, was also later retold by the Roman poet, Ovid, in his poem Metamorphoses.
Later on, other famous European writers wove Theseus into their work. The great warrior-king make an appearance in Chaucer's The Canterbury Tales, Racine's Phaedra, and Shakespeare's A Midsummer Night's Dream and Two Noble Kinsmen. These days Theseus is still kicking it. He's shown up in everything from B fantasy adventure movies, to cartoons, to TV shows, and video games like God of War II. He's got his own movie: the 2011 epic adventure, Immortals. This movie doesn't have a whole lot to do with the original Greek myths, but, hey, it's from the guys who made 300, so it's probably going to rock.