Information about the day here and here. It's the halfway point of Lent, and our linebacker-sized priest always comes up to our station chapel dressed unapologetically in rose-colored vestments. The name comes from the beginning of the introit: "Rejoice, Jerusalem!"
Usually during the year we go once every one or two weeks to the local market where the kids get to buy candy or a soda. During Lent we don't do that, but on Laetare Sunday we do. It has become a family custom, and gives them something to look forward to as Lent begins.
I love the way the Church understands our psychology. As a convert I didn't find out for years that Sundays were counted as "little Easters" and not Lent. I would give up something, like chocolate or meat, that was important to me, and inevitably fail horribly by Easter. I am sure it was good for me to fail like that, but it was also good to find out in due time that once the sun falls Saturday (our only Mass up here is the Saturday vigil mass) we can, for 24 hours, let go of our Lent. That of course doesn't mean making up for lost time, but it is fun to have something we are usually denying ourselves. In my case that would be coffee and chocolate!
And Laetare Sunday is even better because it specifically marks a respite, a waypost before the last part of the journey:
In Rome, Italy, the Holy Father Pope Benedict XVI will bless a golden rose “representing Christ in the shining splendor of His majesty.”
The golden rose is customarily conferred on churches, shrines, cities, or distinguished persons as a token of esteem and paternal affection.
“The shift to a joyous mood is meant to encourage the faithful to persevere fervently to the end of this holy season, as well as to focus on the hope and rejoicing that the Resurrection of Christ, which will be celebrated on Easter Sunday is near.”