Split is a really easy Linux command you can use to split large files into smaller chunks.
Split is quick and painless to use, this is how you split a 800MB file into 100MB chunks with the prefix splt_:
split -b 100m fileName.avi splt_
The -b is the bytes option use 'm' for megabytes. The above will result in a number of files named splt_aa, splt_ab, splt_ac
You can put the pieces back together with cat
cat splt_* > fileName.avi
Tips And Tricks
Remember that if you plan on burning the files to DVD you should keep the file size to under 2GB to keep compatibility with ISO standards.
Gnome Split is a niffty little GUI that acheives the same thing.