Look at this :
... If the cd is not completely broken into 2 or more parts, stick a thin tape on the label side and put the cd in the drive. Download and install the CDRWIN demo application. The demo app limits the cd operations to 1x. But you dun want this app to do anything. Just install and run to make the cd spin at 1x. This low speed prevents the cd crack from expanding. Now open the cd drive contents window and hope that the window shows up at least some contents. If it does :D copy the ones that are readable.
I employed this exact method to recover a lot of data from a badly cracked CD! ...
Im not sure if it works but it doesnt sound reasonable might aswell give it a try!
And the thing i read about is for scratched cds not broken ones, here it is anyway :
http://www.wikihow.com/Repair-a-CD-With-Toothpaste
Hope this helps.