Check out the recommended items at each of those places. You will typically find a link to recommended items on each of their websites. You can also do a quick Google search and find great lists that might be more "put together" than a smattering of responses here.
I agree with PP that sometimes the recommended list is a little overboard! I registered at Target and I personally love how theirs is set up. There are a few items that I knew we didn't need, so in my "checklist" section of the registry, there are some blank spaces.
I put something together based on the store checklist and then had an experienced mom friend look it over and tell me what was unnecessary/brands that she preferred/etc.
Re: What to register for??