There are some USB<->IDE chipsets supported. At work we have an elcheapo generic USB enclosure and it's supported just fine by kernel 2.4.18 in RedHat 8. You might check
http://www.linuxusb.org/ and see what is supported. Generally though the controller chip is what will be supported, not a particular brand box. Whatever Iomega uses internally they probably buy from some company which makes USB controller chips...