All three of my original drives are "in the field" now. I just received four more today and I'll be scattering those about as soon as possible.
I found a "travel bug" in my brief geocaching adventures after dropping off the second drive. For those of you who aren't familiar, it's a small dog tag with unique number on it. Geocachers pick them up and move them from cache to cache. Since it was already on a keychain, and because I wanted to increase the probability that I would at least hear something about one of my drives, I attached it to the third before dropping it off in a cache.
Anyone interested in tracking the tag (and possibly the drive, assuming they remain together) can do so here.