Thaipusam is a festival celebrated by the South Indian Hindu community. These pictures show the 2005 festival in Singapore.
Thaipusam is devoted to the worship of Lord Muruga and involves processions during which devotees carry huge shrines with sharp metal spikes and lots of hooks called kavadi, which pierce into their bodies. Some wear shoes of nails or pull along heavy shrines with religious images and iconology through hooks pierced into their torso. There are also many who have sharp piercings through their face or fruits hanging from hooks pierced onto their chest. Through religious faith and trance, very little blood is shed and the devotees endure the pain to march a certain distance (4km in Singapore) as a sacrifice to the gods. Other devotees carry vessels of milk on their heads or shoulders to be presented to Lord Muruga at the end of the procession.
In modern, hi-tech Singapore, even lawyers, engineers or IT professionals put aside their sophisticated everyday life to put on the kavadi to show their devotion to the gods. There are also many who participate to fulfill their promises.

This site has some more links:
http://whatsonwhen.com/events/~25114.jml