XIcons.com, a great source for a number of OS X friendly replacement icons, has released a new set of hard drive icons. Most OS X users have both and OS 9 and OS X volume available from within OS X. Sometimes, at a glance, finding which drive is which can be confusing. Not with these cleverly designed icons, however.
Featuring the standard OS X internal hard drive icon, the new icons offer a superimposed "X" symbol or "Classic" symbol over the drive, allowing for another subtle visual cue as to which drive is which.
You can download these icons, and a host of other great OS X friendly icons, at the XIcons web site.