There are plenty of festivals going on in Hong Kong, especially because the population is so diverse.  The list below represents many of the major ones, and the Hong Kong Tourism Board has a list of upcoming ones online at:
www.hkta.org/eng/showtime/festivals

Chinese Arts Festival
Hong Kong, SAR, PRC
(852) 2734-9009

This festival is celebrated every two years (on even-numbered years) to focus on the talents of Chinese artists from all over the world. The festival takes place in late October or early November and has all types of performances and productions in the arts.

Chinese New Year
Hong Kong, SAR, PRC
(852) 2508-1234

This is the biggest Chinese holiday. The Lunar New Year occurs in January or February and is celebrated with horse races, flowers, and fireworks. During the holiday, nearly all shops are closed.

Dragon Boat Festival
Hong Kong, SAR, PRC

This Dragon Boat Festival takes place on the fifth day of the fifth lunar month, which means sometime in May or June.  It commemorates the death of Qu Yuan, a Chinese hero who drowned himself in protest.  There’s an elaborate boat race with a thumping drum soundtrack, and many revelers jump into the river.

Hong Kong Arts Festival
Hong Kong Cultural Center
2 Harbour Rd
Hong Kong
(852) 2824-3555

This festival begins late February ends four weeks later in March.  It features art from around the world, and includes theatre, music, and drama performances. The Hong Kong Cultural Center is the main venue for the displays, but there are performances in other locations too.

Hong Kong Folk Festival
The Island School
20 Borrett Rd
Hong Kong
(852) 2813-1445

This cultural festival takes place over a weekend in November.  The folk artists that are featured are usually local entertainers.

Hong Kong International Film Festival
Hong Kong, SAR, PRC
(852) 2734-9009

This two-week long festival in April features both local and international films.  The movies are from up and coming directors, Academy Award winners, and everyone in between.  You can purchase tickets at the door, but if you want to see one of the bigger films, you should try to buy tickets in advance, because they often sell out.

Mid-Autumn Carnival (Moon Cake Festival)
Hong Kong, SAR, PRC

This holiday celebrates both Confucius’ birthday and a 14^th century uprising against the invading Mongols.  During the festival, paper lanterns light the cities, and children eat special cakes known as Moon Cakes, as the autumn moon rises.

Spring Lantern Festival
Hong Kong, SAR, PRC

This festival takes place on the last day of the Chinese New Year (in February) and is sometimes called Chinese Valentine’s Day. Lanterns are hung in people’s homes and in the streets.  Ko Shan Park is the center of events celebrating this holiday.