Others have also mentioned "free-standing" internal drives used externally (via USB connections).

Like these:

"PCMS IDE TO USB 2.0 DRIVE 2.5"/3.5"/5.25" ADAPTER PC/MAC"
http://www.pcmicrostore.com/PartDetail.aspx?q=p:10501935

"SABRENT USB 2.0 TO IDE CABLE FOR 2.5"/3.5"/ 5.25" DRIVE WITH POWER ADAPTER"
http://www.pcmicrostore.com/PartDetail.aspx?q=p:10502660

"BYTECC IDE TO USB 2.0 ADAPTER FOR 2.5 / 3.5 / 5.25IN DRIVE"
http://www.pcmicrostore.com/PartDetail.aspx?q=p:10502715


With the prices of HD's, I'm thinking of using these type of connectors with HD's as backup drives - forgoing the case altogether.