It depends on what you need to do with the pieces. If all you want to do is break the file into smaller pieces, there always /usr/bin/split. If for example you wanted to split an avi file called big.avi into pieces no bigger than 500MB, you could use something like
Code:
/usr/bin/split -d --bytes=536870912 big.avi big.avi-
This would output files of 500MB in size called big.avi-01, big.avi-02, etc.
To put them back together again, you just cat them, e.g.
Code:
/usr/bin/cat big.avi-01 > big.avi
/usr/bin/cat big.avi-02 >> big.avi
This last part should go in a loop - you don't want to be doing that manually...