SleeplessHD

I haven't tried this but it could be handy for some of you. SleeplessHD is a tiny app that tries to keep your Hard Drives from spinning down. You can set the spin down for your Mac in general in System Prefs but a few external HD's out there have odd firmware which will still spin them down no matter what you tell them.

SleeplessHD is one solution for this kind of problem. Try it! It is free and has this fancy smoking Dock icon animation...