It is a spring festival, of religious origin celebrated by the Hindus, during which people will throw colored powder and coulored water at each other. The date usually falls by the end of february and beggining of march.
The colored powders, that can be seen in the markets exposed in metal bowls, are traditionally made of Neem, Kumkum, Haldi, Bilva and other medicinal herbs used by Ayuverdic doctors, and the whole activitie of throwing colors at each other has a medical significance to the participants, since this time of the year comes with weather changes that may cause illness.
I find it amazing, the whole aspect of the festival of colors, having a time of the year to remember how bright and cheerful life can be even when things go bad. I miss color sometimes, seems like more and more we have this need for everything to look sharp, and spotlessly clean to look fancy or whatever. And I look out the window and I see an entire city painted grey, black, white and shades of beige. Makes me so happy when I walk by a little hidden street and suddenly there's a colored house :)
As a matter of fact, there's actually a project going on in Brazil by a paint company that I found so genius. They go arround painting historical parts of the cities in many different colors. It's so pretty, take a look http://www.flickr.com/photos/coral-brasil/
And if you wanna discover more about the Day of Holi, you can check Holifestival.org and Wikipedia ;)
Ps: Peeps, you're too quiet. Talk to me so I can talk to you :)