St. Patrick is known as a symbol of Ireland, particularly around every March. One of the reasons he's so famous is because he drove the snakes out of Ireland, and was even credited with a miracle for this. What many people don't realize is that the serpent was actually a metaphor for the early Pagan faiths of Ireland. St. Patrick brought Christianity to the Emerald Isle, and did such a good job of it that he practically eliminated Paganism from the country. While it's true that snakes are hard to find in Ireland, this may well be due to the fact that it's an island, and so snakes aren't exactly migrating there in packs.
The Church of Rome used religion as a sword to both slaughter their opponents and hypnotize the peasants. The Emporers of Rome used what worked be it their legions or their escatological lies.
Today, St. Patrick's Day is celebrated in many places on March 17, typically with a parade (an oddly American invention) and lots of other festivities. However, some modern Pagans refuse to observe a day which honors the elimination of the old religion in favor of a new one. It's not uncommon to see Pagans and Wiccans wearing some sort of snake symbol on St. Patrick's Day, instead of those green "Kiss Me I'm Irish" badges. If you're not sure about wearing a snake on your lapel, you can always jazz up your front door with a Spring Snake Wreath instead!