we rarely give a straightforward answer that everyone agrees on. Well, I am immediately going to disagree with Bingley (!) and say that his answer is unequivocally correct. I would like to add my welcome, also, heni.
oftroy, also known as Helen (how could we help it?), gave you some good examples. I can only add that the verb must agree with the subject, and in your sentence, the word 'one' is the subject. One is. Many are. If you, for example, wanted to list your hobbies, you would put, "My hobbies are: reading, bicycling, and (watching, as Helen said, is implied) soap operas".
You could also recast your sentence as: "I have many hobbies; one of them is soap operas". Hmm--in a way, this is similar to your sentence; you wrote 'hobbies is', and I wrote 'them is'. To
me, mine makes it clearer that the verb should be singular to go with 'one'; however, I am belatedly realizing that it may not be clearer to a non-native English speaker. Oops!
However, let me congratulate you on your acquisition of the language; to have gotten so far as to question this--a topic we have had disagreements about, ourselves--shows a great understanding.
