I have been encouraged by many people to start a registry earlier rather than later. It makes sense to me because I know that I will inevitably forget something really important the first round. I have been slowly adding items as they come to mind. Currently I have a hodgepodge list on MyRegistry.com. I actually love the site as it allows me to register for items not at Target and Babies 'R' Us. However, it also has the ability to cross reference with registries at brick-and-morter stores (which is good because Ben is looking forward to using the scanner at Target).
The next big decision is disposable vs. cloth diapering. We're leaning toward cloth, which would mean I get to determine the brands and amounts we are going to need... what fun that will be.