My clamshell ibook can handle which videoformat?

First of all, please excuse me for any mistakes in my written English, as it is not my main language.

So here I go:

Now that I've upgraded my ibook tangerine with a 120GB harddrive, I want to store some movies on it in a format that my ibook can handle.

I will use my macbook to rip a few dvd's and convert it to the proper videoformat, but the question is, which videoformat? I suppose that my ibook can't handle divx, xvid and plain dvd's.

My aim is to be able to watch some tv series on my ibook (ripped from my dvd-collection), that's all, it doesn't have to be high quality, just watchable and without, if possible, frame drops.

Can anyone point me to the right direction?

Thanks in advance!

I'm running 10.3.9, with 128Megs of ram.
My experience is that VLC is a little bit too heavy for my clamshell ibook.