I personally love and recommend Hotslings (hotslings.com). They're a little on the pricey side, but not terrible-and you can usually find them on ebay slightly used for less. You can use them from birth, but I got mine when my youngest was 8 months old, and it was well worth it then. I actually got 2 (they come in all different patterns and fabrics), and ended up giving them both away to friends. I wish I hadn't because I could still use them for carrying my 3 year old when we go out for long periods.
There's a local store that sells them near me, so now that we're going to have another little bean joining us, I can't wait to get over there and get a new sling.