Instead of ordering a new battery, you may want to consider getting a recharger such as the Tekkeon TekCharge MP1800. For less than the cost of a new battery, this little device will recharge the Droid, Eris and just about any other phone.
I was all set to get a new battery, until this met my need for additional power. I use this when I don't have extended access to AC or car power, such as in a meeting, or I'll connect it up with the Droid and leave it recharging in my briefcase/backpack on my way somewhere. When I show up, the Droid's fully powered.