If you are talking about real physical read speed, then the EPO 58X IDE CD-ROM is the fastest that I know of. However, that speed rating may just be an up-rated 56X drive, measured at 58X max at the end of an 80min or 90min CD.
I still have my Afreey 56X (max) IDE drive, and love it, although I don't think that you can find them anymore. (52X max now). It once glitched during some testing that I did, and it actually spun up to 60X max speed! I suppose, therefore, that it might be possible to hack the firmware to do that all the time, but I don't think it would be worthwhile. The increase in noise going from 56X to 60X was substantial, I thought that I might shatter actually shatter a CD for once. (Thankfully, it didn't, and I have never worried about it running it at 56X speed either. Most media I have isn't high-enough quality to rip at 56X anyways, so I go for a 32X P-CAV rip speed.)