Today is the Jewish holiday Tu B'Shvat. The words Tu B'Shvat mean the 15th day of the Jewish month Shvat. It's also known as the New Year or "birthday" for Trees, kind of a Jewish Arbor Day. Tu B'Shvat is the new year for the purpose of calculating the age of trees for tithing. 

The Torah states that fruit from trees which were grown in the land of Israel may not be eaten during the first three years; the fourth year's fruit is for G-d, and after that, the fruit can be eaten. (Leviticus 19:23-25) Each tree is considered to have aged one year as of Tu B'Shvat, no matter when in the year it was planted. 

This holiday is one of the minor holidays so it does not require fasting or other observances that the major holidays require.   Tu B'Shvat is usually observed by planting new saplings and having a ritual meal similar to the Passover seder, with the focus of the seder being fruits and nuts that come from trees.

The proper blessing before eating any fruit is:

Baruch Atah Adod-nai Elohai-nu Melech HaOlam boray pri ha-aitz.
Blessed are you G-d, King of the Universe, Who creates the fruit of the tree.

On Tu B'Shvat, it is also customary to eat a new fruit (a seasonal fruit that you have not yet tasted this season), and to say the following blessing:

Baruch Atah Ado-noi, Elohai-nu Melech HaOlam, sheh-he-che-yanu vi-kee-yimanu vi-hee-gee-yanu laz-man ha-zeh.
Blessed are You G-d, King of the Universe, Who has kept us alive, sustained us, and brought us to this season.

Today is a great day to taste a new fruit, and plant a tree.  Bring home a fruit that you've never had before and enjoy.