how cracked?
if just cracked - give it a go - copy what you can to your HDD
cd/dvd are quite resilient - even if broken in half - if you can sometimes join the two halves using a thin strong membrane (medical tape is good) and recover some data
stick the tape on the top (not the shiny underside)
however you do it - it's a case of try and see (no guarantee).
if that fails you could try araldite ... but you have to be careful
now for the I told you so
back up the others before you need to