Or Passover to most people... It begins tonight at sundown and continues until sundown on April 20th. Basically, this means that for that entire period I'll be eating "kosher for Passover" stuff or matzah instead of bread and on the first (and sometimes the second) night, there's a Sedar, which is a ceremonial meal recalling the Exodus, fulfilling the commandment of Exodus 13:8.
The commandment especially says to tell the children, so children are very involved in the meal... There could be a practical reason for this too because a two hour long (or longer) meal can be very difficult for little children, and even some big children, if they aren't entertained. It starts with blessings, there are four cups each of Kosher wine consumed by all the adults (and one, usually very slowly, by older children - at least in my house :D - and grape juice for younger children) (a fifth glass is set aside for the Prophet Elijah, who is said to visit every Jewish home during the Sedar, but we'll get to that later), the symbolism of the foods on the Sedar Plate are explained, bitter herbs, matzah, and a mixture of apples, nuts and wine (called haroset) are eaten after more prayers are said, the story of the Exodus is told (in brief), a piece of matzah called the Afikomen, is hidden somewhere in the house for children to find after dinner (kinda like looking for eggs on Easter), and the youngest child present (or youngest that is able) asks the "Four Questions" in Hebrew. (Note: All the aforementioned is not necessarily listed in the order of how it happens. It is explained much better here: http://www.holidays.net/passover/seder2.htm or here: http://en.wikipedia.org/wiki/Pesach)
Then the actual meal begins, usually with a hard-boiled egg, some gifelte fish, and a bowl of Matzah Ball soup (or "Bubbe's Chicken Soup" as my little brother would always call it.). After that, it goes on to perhaps a salad and the main course, usually a meat dish of some kind (chicken or brisket generally), with vegetables and more matzah, haroset and whatever else because it's good. Now, in my house, though it's not strictly according to the rules, the rest of the Sedar is done over coffee and dessert (usually "Kosher for Passover" cakes or assorted maccaroons). Grace is said (Jews say Grace after a meal and not before, if at all, but especially on Passover as part of the Sedar), there's the fourth glass of wine, the children go open the front door for the Prophet Elijah (while they are gone, it's not uncommon - at least in my parents circle of Jewish friends - for one of the adults to drink Elijah's cup down a bit, so that when the children come back, they see that something actually happened to it), and then the Afikomen search begins. Many times, the child who finds it gets a prize of some kind (a dollar, a piece of candy... some kind of trifle) and they get to eat that piece of matzah. Some groups, who want to keep the peace and not have arguments or tears, break the Afikomen into several pieces so that all the searching children can find a piece of it.
Passover is my favorite religious holiday because what more can you ask for? It's a meal of good food and good wine with friends, recalling a time of joy, children learn of their history and adults remember it. It's a perfect holiday! To me anyway... And my favorite hymn in the world, the Michamocha, is *the* Passover song (or should be, since it's the song that the Hebrews sang after crossing the Sea of Reeds, even if it is more closely associated with Shabbat today, and other than Dayenu [I would love to link to it, but I can't find a place on the web that has all 15 stanzas! ... How's that for a road-trip sing-along song? I learned them all when I was little, but seems that got too annoying for parents to listen to or all of them aren't considered PC enough for today's parents ::rolls eyes::], which was my favorite as a child). Couldn't get any better... (I also really like Adon Olam and Maoz Tzur [the original, 900-year-old "Rock of Ages," translated into the commonly known English hymn about the mid-19th century.])
More information can be found here: http://www.jewfaq.org/holidaya.htm Although, I personally don't follow the stricter rules that are described there. My educated opinion is that they are taken far further than necessary. http://www.holidays.net/passover/ is also an pretty good source of information, especially for the Reform tradition.