Here's another video from Chabad in India, from one of the other Chabad Houses, a bit south of Mumbai, showing the sorts of things they do. Like, hang out, dance, sing, put on Tefillin, celebrate Chanukah (coming up again soon), hang out, dance, sing, observe a brit milah (circumcision ceremony), hang out, dance, sing, celebrate Purim (when it is obligatory to get drunk, no joking), hang out, dance, sing, and also, did I mention? Hang out, dance, sing. The rabbi in the video is the guy on the motorcycle and also handing out Chanukah donuts.
The reason they hand out donuts is that donuts are made with oil, and the miracle of Chanukah was that the olive oil lamps of the temple menorah candelabra miraculously continued to burn, signifying that the other extraordinary events, the victory over the Greek oppressors, was also by the hand of G-d. Oil has two contradistinctive properties. On one hand, it has a tendency to spread out, touch, cling and coat everything. Oil on a salad will tend to cling while water may splash off. Oil can even be absorbed into some rocks that will not absorb water easily. This signifies the idea of spreading out and being involved with the world to improve it. But oil also has another property, it remains separate from water and will rise above it. Hence, it signifies remaining true to your beliefs and not corrupting or compromising them even while being involved with the world.
The reason Hassidim are always making merry and celebrating, as you can see in the video, is from the statement in the Bible, Nehemiah 8:10, "Rejoicing with G-d, that is your strength."
http://www.youtube.com/watch?v=E1xx8hZeols