how to split an .avi file in two?

Basically i'd like to know how i would be able to split a .avi file into two parts? Like, say i have a 1gb file i would like to split into 500mb each, or if i wanted to edit a file by taking out the useless fodder in the beginning/middle/end (or even taking out a UseFul clip from the b/m/end)....

O and, obviously, this would have to be a Mac app...

Thanks in advance for any help!