New at Mac

Hi, 

I just bought an i-book, which for me new also because I never used
any mac before. So I am not so good at it for the moment, and I need
some advices
- first I would like to download some movies, or music, could someone
give a website like kazaa where I can do this with my mac?
- second I would like to download some math, stat softwares and also a
scientific text editor...same question as above...do you know where I
can find some?
- third...I really like a baby with this mac, so if you have any good
information that will make my mac better (or me with it)...please go
ahead...

Thanks a lot,

Olivier