The word "Khalsa" means "pure", Khalsa's are Sikhs which have undergone the sacred Amrit Ceremony initiated by the 10th Sikh Guru, Guru Gobind Singh.

The Khalsa baptism ceremony involves drinking of Amrit (sugar water stirred with a dagger) in the presence of 5 Khalsa Sikhs as well as the Guru Granth Sahib. The initiate is instructed in the following;

I have been following the various initiative started by Sikh Coalition.
Recently they have come up with http://www.khalsakids.org/.