Officially the longest day of the year. For those like me who dont mind sleeping in until afternoon, it is great. Because the sun doesnt go down until late and you don't feel like such a p.o.s for wasting the whole day. But what does it all mean?
Fun Facts about the Summer Soltice:

Sol + stice derives from a combination of Latin words meaning "sun" + "to stand still." As the days lengthen, the sun rises higher and higher until it seems to stand still in the sky.

As a major celestial event, the Summer Solstice results in the longest day and the shortest night of the year. The Northern Hemisphere celebrates in June, but the people on the Southern half of the earth have their longest summer day in December.

The Celts & Slavs celebrated the first day of summer with a bunch of Hippie crap like dancing & bonfires to help increase the sun's energy. The Chinese marked the day by honoring Li, the Chinese Goddess of Light.

Perhaps the most enduring modern ties with Summer Solstice were the Druids' celebration of the day as the "wedding of Heaven and Earth", resulting in the present day belief of a "lucky" wedding in June

Pagan spirit gatherings or festivals are also common in June, when groups assemble to light a sacred fire, and stay up all night to welcome the dawn.

No matter how you choose to celebrate, just get your ass outside and enjoy the sun!