Where can I find a 15,000 rpm harddrive? What about a 20,000 rpm cdrom drive?

CDRom drives are not measured by RPMs because they use variable RPM speeds with Constant Linear Velocity (CLV) or nearly so. You can buy a 52X cdrom drive, which is the fastest "safe" drive.

Using newegg.com, I found several 15k RPM drives. They are all SCSI and range in price from $208 for 36 GB to $1200 for 147 GB. Enjoy.

Seagate, Dell, Fujitsu and others sell them, but I hope you have SCSI connections at at least $1000 to shell out for it.

As an FYI, RAID gives much better performance/price tradeoff than the superfast hard drives.

Also FYI, please try to use a more descriptive title in future. Your title told us nothing at all about your question and is, really, misleading.

A 15,000 RPM hard drive just consumes more power than slower RPM hard drives. Hitachi's T series SATA hard drive is faster than Western Digital Raptor series even though Hitachi T series drives has half the RPM speed and more than quadtruple the capacity at the same price.

As the spindle speed gets faster and faster. It will produce more errors. 7200 RPM is about the maximum speed for minimal errors during read and writes. Also a slower RPM drives can squeeze more gigabits per square centimeter than faster RPM drives.

The above goes true in CD-ROM drives. A 52X or 72X CD-ROM reader will sound like a jet engine, but it can have a lot of problems reading the medium. On some drives the advertise 52X speed can be either the result of calculating the RPM of the outer edge or a speed that can only be met when the universe is in alignment which means an unrealistic value.

CD-ROM speed > 52x can be DANGEROUS. The plastic in optical discs can come apart at these speeds.