Oh good. I was reading through and had a bunch of ideas and got to the sling and said yes, sling, those are awesome! and no don't worry you don't have to get a specific size! (all of these were expressed internally mind you), and then got to the last post, yay. I loved mine. One of those pre-baby presents I got that I wasn't that enthusiastic about and then became a prized possession once the baby arrived.
Another thing (just for the record) that I love is a set of mirrors so you can see your baby in the backseat while you're driving. I need it because I'm deaf, but every mom I know who's seen my mirror(s) (needed two when she was rear-facing, one once she turned around) has thought they were really cool and useful. Several bought them, just to be able to see the baby while driving, even though they could hear the baby too.