I'm starting to jog, and wanted to find a good armband case for the Droid. I got this one: Tune Belt Sport Armband for iPhone, Palm Pre, Blackberry Storm and More The phone fits well. The case is not completely enclosed, so if I run in weather I'm going to try to figure out how to wrap the phone or armband in a ziplock or something. Otherwise, the screen is completely viewable in this case, and the screen is still quite responsive through the plastic cover. The attaching strap is big, and it has a small tab to manage your earphone cord (if you're not using bluetooth). I like it.
If you can find one of these, I think it would work pretty good. iBike Rider case for iPhone aims at bikers, people with their arms full -- Engadget
A lot of us long-distance motorcycle tourers rely on Otter Box to weatherproof our devices. They don't appear to have a DROID cover on their site yet, but perhaps you should email them to see when it's getting released. They make top-notch quality gear!
Otterbox rocks! Had one of their cases for my iPhone and my iPaq. This one might work for the Droid. 2600 Series // 2600 Series PDA Case // OtterBox.com
