Let me make a list -
Reading and collecting books. I love collecting old books especially various editions of the same book. For that I move around the old book stores of my city at length.
Listening to music and collecting Cds. My father has a huge collection of LPs and he still collects them. I love playing them too.
Watching movies of various genres and of various languages. My sister & I have made a collection of over 8000 titles.
Learning new languages. At school other than the mandatory learning of Bengali (my mother tongue) & English, we had to take two more optional languages of our choice (obviously from the options present at school). So I took Sanskrit & Hindi. After school, while at college, I pursued French & Japanese. Now I am pursing Persian & Urdu. Later, I have plans for more.
I like to sketch. I use charcoal for that and sometimes dry pastels. I love to paint also. I prefer water-color over oil-paint because I love the fluidity and the transparency.
Collecting stray animals and taking them to the shelter where I work as a volunteer. Some of the strays I have kept at home with whom I have a special bond (they are like my children). I love taking care of them. In this matter my whole family works together.
One more thing. I love to play the violin. I have taken music lessons (violin playing) for 12 long years since the age of 5 1/2. I have graduated from the music school with a distinction.
I am a philosophy major. Recently my dissertation for my pre-doctoral entrance has got approved by the doctoral research committee of my university. So from now on, I'll be able to work on my doctoral thesis for the next 3 1/2 years. I'm looking forward to it. I don't know if I can call this doctoral research part as my hobby or not, but I am very happy and excited to work on it