The Initio "IT-B2" bridge board inside my ADS Tech Firewire 800 external drive kit can actually support two ATA devices, not just one. It's not mentioned anywhere in the manual, of course. The "IT-B2" board contains two large chips, and a number of small ones. The largest one is the Initio 2430L, which provides the Firewire 800 interface. The second-largest is the Texas Instruments TSB81BA3, which provides the IDE interfaces. The board looks almost exactly like this. If you clip the wires that join the board to the power supply in the ADS case, you can remove it and reinsert it into any other case, even the monstrosity pictured above. Screw it into the opening where a Centronics SCSI connector would usually go, hook the +12v wire into the power supply, and you've got yourself another Firewire 800 external drive.
Why am I doing this?
With a second Firewire bridge board installed in the same case, I can create a FOUR DRIVE RAID 0 ARRAY, fed via DUAL Firewire interfaces, into my Powerbook. At current hard-drive prices, that's a disturbingly fast 1 TERABYTE external drive for about $500.
Actually, since I already own two 200GB drives, the case, and one bridgeboard, my total outlay for an 800GB array would be about $200. Currently, the two drives are enough.