The official first day of summer; and a full moon tonight. Flowers are in bloom; berrys are in the fields; bees are a buzzing; birds are a'nesting; and it is the longest day of the year [ref. 2], as the sun is in the "tropic of cancer" [ref.2].

At last summer, a time to celebrate, at least in the Northern part of the world.

According to someone, [ref.1], this is the "Honey Moon" because you are supposed to go fetch the honey from the bee hives.  I wouldn't recommend this if you aren't good with bees, I tend to fetch it from the grocery store.

However, this is the reason so many people are married in June; because it is time when fertiity of spring comes full circle; and people go on there "honeymoon"; get it? I do... [ref. 1]

Almost every religion and culture built a celebration around this glorious light filled day. Religiousolerance.org [ref.1] has a great run down on each one.  Most are based around fertility and celebration of the light.

Selena Fox, a Wiccan practitioner, recommends celebrating the Goddess by staying up the night before and welcoming the sun in the morning.  Then chant and dance with your friends, burn a yule wreath, give some gifts, and play the bongos for a while.  Sounds like a good party.  [ref. 2]

I also found an interesting essay about the soltice from G. D. Purucker.

"the event of the Summer Solstice, at which time the neophyte or aspirant must undergo, and successfully prevail over, the greatest temptation known to man just referred to; and if he so prevail, which means the renouncing of all chance of individual progress for the sake of becoming one of the Saviors of the world, he then takes his position as one of the stones in the Guardian Wall. Thereafter he dedicates his life to the service of the world, without thought of guerdon or of individual progress -- it may be for aeons -- sacrificing himself spiritually in the service of all that lives. For this reason the initiation at this season of the year has been called the Great Renunciation." [ref. 3] 

From The Four Sacred Seasons by G. de Purucker. Copyright © 1979 by Theosophical University Press)

ref. 1 http://www.religioustolerance.org/summer_solstice.htm

http://scienceworld.wolfram.com/astronomy/SummerSolstice.html

http://en.wikipedia.org/wiki/Summer_solstice

ref. 2 http://www.circlesanctuary.org/pholidays/SummerSolstice.html

ref. 3 http://www.theosophy-nw.org/theosnw/seasons/4s-gdpsu.htm