Though it is technically a minor holiday, Lag B’Omer is actually quite loved by most Jews, especially Israelis, who travel all the way to the north, to Meron, to the grave of Rabbi Shimon Bar Yochai to celebrate with bonfires, music and dancing, baking potatoes and onions in the fiery coals. In the morning, the mountain becomes giant prayer field, and upsherin ceremony (the first hair cutting of a 3 year old boy) is performed on all who qualify. Those who have been there have described the experience to me as mystical.
Rabbi Shimon Bar Yochai declared that people should rejoice on his yartzeit, which is why we have these celebrations. The fires are a symbol of the Zohar, the primary book in Kabbalah, the study of the esoteric secrets of the Torah, a book composed by Bar Yochai after 13 years of hiding in a cave, escaping from the Roman authorities, meditating and communing with the Ein Sof (Divine infinite).
We had a party last night at our shul (click on the pic above to see the set) where we had a BBQ (yum!), music and dancing, and where we lit torches in honor of 12 tzadikim and one in honor of all Jewish People. It was fun.