According to the Abilene Reporter News, it's time to don your finest and stuff yourself with desserts!
During this 10-day celebratory time, you're not supposed to look at the moon. The moon laughed at Ganesh, when he fell off his rat (among other reasons), so don't give it the satisfaction of your gaze.
One of the gajillion versions of his story (the first one I heard) tells that Ganesh was born to Parvati, wife of Shiva, who was off fighting in a war. When he returned to find his wife cavorting with a young, handsome man, he drew his trident and beheaded him. When dad realized his mistake, he cried to Parvati that he would go into the forest and replace his son's head with the first animal he could find.
Buddha was a Hindu, and the Bhuddists call him Vinaayaka. Vignesha means "Lord of Obstacles" (vighna is sanskrit for obstacles). As in, the one who sets them up and brings them down.
Once in Kathmandu I watched some kids my age giving puja to a Ganesh statue. I asked my friend (who spoke more fluent Nepali) what they were doing - he said they were preparing to take their exams.