I'm currently using CF in most of my older macs:

http://synack.net/~bbraun/idecf.html

The SCSI based systems are using the R-IDSC-E adapter linked to earlier, with my experiences documented here:

http://synack.net/~bbraun/ridsce.html

I've gone the SCSI-IDE-CF adapter route instead of the SD card route as CF is basically a straight through connection to IDE, so only one level of translation is occurring (SCSI-IDE). There are enough variables in this setup without adding IDE-SD translation to the mix IMO.