I've found that it's easy to hit the volume rocker and silence my Droid by mistake. But the rocker switch is more convenient than going into an app, or even tapping a widget, so I don't want to use any of the volume control apps I've seen. I wrote a new app called RingGuard, which is on the Market for free. It's been well-received on a couple of the other Droid sites. Here's the description:
Guard against unintended ring volume change, while allowing normal use of volume rocker switch.
When volume is changed, a confirmation dialog pops up. Can confirm on screen, or with hard keys. After a configurable timeout, volume is restored to original setting.
Tested on Motorola Droid.