Tekram D690CD IDE PCI Cache Controller (with RAID level 1 Mirroring and caching)
ARCO Inc. DupliDisk IDE disk mirroring controller
Support for ATA, IDE, E-IDE and UDMA drive. Controllers available can be plugged into ISA and PCI slots, and directly into the IDE controller. Furthermore, 3.5-inch and 5.25-inch Bay Mount units are available that fit into the respective drive bays. More information at Arco's web site. Make sure you have at least rev 3.00 of the firmware.
Mylex RAID controllers
More information can be found here.
3ware Escalade IDE RAID controllers
3ware's 5000-series and 6000-series controllers have been supported since kernel 2.2.15. For more information, see 3ware's web site.