As long as the plastic hasn't dry-rotted, the older ATA33 cables should still be fine for your CDROM or burner. Very few optical drives go beyond ATA66 (Pioneer DVDROMs comes to mind). So long as you don't Master/Slave an ATA66/100/133 HDD on the same IDE channel, these old cables can still be of use. I wouldn't chuck them away.
The only problem I see with standard ATA100/133 ribbon cables is that they're only cheap if you buy them online and in bulk. Factor in the shipping, you wind up paying $8-10 (or more) for a single cable. Prices are also a rip-off at all the retail places such as Staples, CompUSA, Circuit City, etc.. That's why I always horde all the spare cables that come with the motherboards I get.