Heyyo,
Yes, with CD-RW's. You can always re write to those cds.. BUt, if you wish to change content already on the cd (such as replace a file) you need to erase the current content on the cd. So I'd be like this:
finish some course work, burn it to a CD-RW.
You update that course work, back up the course work on the CD-RW (like files you'll still need that won't be updated) onto the HD that you might wanna re-write to the cd-rw.
Erase the CD-RW
burn the new files onto the cd-rw.
the process repeats.
Most CD-RW's are 650MB, and note they are more expensive than CD-R's due to their ability to re-write. Also note that you can't use them for music cd's as a music cd requires the CD to be "finalized". Why? who knows, some crappy standard for CDA's I guess.