True Cross - I'm sure there are enough alleged pieces of this that the True Cross would have to have been the height of a skyscraper in order to accommodate all of them. I once heard a joke that the reason there are no more cedars in Lebanon is that every Crusader had to bring back a piece of the True Cross. The legend associated with the cross says that it, along with those of the two revolutionaries executed alongside Jesus, was discovered in Palestine by Helena, the Christian mother of Emperor Constantine. There's more to it than that, though. The Golden Legend, which was first recorded in 1260 but probably predates that as an oral tradition, has it that the wood was from an offshoot of the Tree of Life, which was used to build a bridge that the Queen of Sheba crossed to visit King Solomon. The king buried part of the timber, and it was eventually used by the Romans to construct the crucifix on which Jesus died. I'll give the framers of this legend major points for creativity, but how likely do you really think all that is?
Shroud of Turin - This was actually in the news recently, as just this month, a professor named Luigi Garlaschelli managed to reproduce the artifact using technologies that would have existed in the Middle Ages. Radiocarbon dating was performed on it back in 1988, and the conclusion was that it originated in the thirteenth or fourteenth century. The first unequivocal mention of the shroud was in 1357, and even in those days it was widely considered to be a forgery. But believers in the shroud are keen to point out potential flaws in such evidence, and maintain that it actually was worn by Jesus. The shroud is one of many cloths said to have made prolonged contact with the body of Christ at some time or other. A church in Spain keeps the Sudarium of Oviedo, which is said to have been wrapped around the head of Jesus' lifeless body. Other purported cloth relics of Jesus' life and death include a seamless coat kept in Germany, a baby blanket located in the same country, Veronica's Veil, and the Image of Edessa. The shroud is probably the most popular today, yet apparently the Catholic Church hasn't even made an official pronouncement on its authenticity.
Holy Chalice/Grail - Sometimes thought to be the same thing and sometimes two different ones, the basic idea behind both legends is that the cup used by Jesus at the Last Supper was preserved through the ages. One version of the Chalice story says that it was kept by St. Peter, then by the popes and the kings of Spain, before finally being turned over to the Cathedral of Valencia where it can be found today. There is, however, a competing claim for the chalice being kept in Genoa. The Holy Grail is thought by some to have been based on confusion between magical dishes from Celtic mythology and the Holy Chalice of Jesus. The Christian version of the story, as related by Robert de Boron in the late twelfth and early thirteenth centuries, has it that the Grail was taken to Europe by Joseph of Arimathea. It is, of course, the object of a quest for King Arthur's knights, and later Indiana Jones and his father.
Spear of Destiny - The Gospel of John adds a detail to the description of Jesus' crucifixion that isn't mentioned in any of the Synoptic Gospels. According to John 19:34, in order to make sure Jesus was dead, a soldier pierced him in the side with a spear. In Christian tradition from outside the Bible itself, the soldier was named Longinus, and the spear the Holy Lance or Spear of Destiny. In the sixth century, Antoninus of Piacenza claimed to have found both the spear and the crown of thorns at Mount Zion. There are several claims for spears being the one used by Longinus, and some stories that say the point and the shaft are now two different relics. The point of this version of the lance was stolen from Paris not long after the French Revolution, while the rest of the spear is being kept in Rome. Another possible Spear of Destiny is the one kept in Austria, which was said to have been used by Constantine, and then handed down by the Holy Roman Emperors. It was part of the Imperial Regalia, and was briefly possessed by Adolf Hitler.
Holy Prepuce - Proving that some of these relic-hunters would go after literally anything they could potentially associated with Jesus, several people claimed to have found the foreskin of Jesus. After all, being Jewish, he WOULD have been circumcised, right? I think the chances that this would have been preserved are even lower than those of the other relics, but since mainstream Christianity holds that Jesus ascended bodily into Heaven, it presumably would have been one of the few earthly remains he would have left. Wouldn't he also have lost a significant amount of hair over his lifetime, though? Seems like searching for that would have been considerably less disturbing, but what do I know?
Relics of Jesus aren't so much in vogue nowadays, although there remain some devotees to the idea. I have to wonder why, even if some of these items legitimately ARE from the time of Jesus, why they would be more likely to have been associated with him than with anyone else. How do the keepers of the True Cross know that it wasn't actually a piece of the instrument of death for some OTHER would-be Messiah? I suppose the most likely explanation would be that, since Jesus is a form of the Almighty God, he would have preserved these items and guided people to find them when the time was right. The story of Helena and the cross, as recorded on Wikipedia, says that she actually found a few different crosses, and God had to indicate which one was the True Cross. But if you DON'T believe in Jesus using miracles to reveal these items (and really, if you were all-powerful, would you want anyone finding your foreskin?), then the odds are very much against finding them. That's one reason why I'm quite skeptical about any story involving the discovery of Jesus' bones. While not universally accepted, the idea that Jesus' body was resurrected and brought bodily to Heaven is the most commonly believed one within Christianity, so Christians presumably think Jesus didn't leave behind any bones. And if you think Jesus was an ordinary guy who died like every other mortal, then his bones WOULD still be somewhere, but how in the world would anyone today be able to tell them apart from any other bones? For some reason, there was a lot of media exploration around two years ago of the possibility that some bones found in an ossuary in Jerusalem could be those of Jesus and his family. The ossuaries were actually discovered in 1980, though, which means this seems to be yet another case of the mainstream media jumping on a really old story as if it's something new and revolutionary.