I second the vote for an Ergo (or Beco Baby). They're kind of expensive, but they can be used for a long time, infant through toddler in a variety of positions. They're very comfortable for mom and baby. Another similar but less structured (and less expensive) sling is a Mei-Tai. They also offer a variety of positions, but may not be able to hold quite as much weight as an Ergo due to construction.
I've also used a Hotsling and a standard Bjorn. They're ok, the Hotsling is really quick and easy, but my 12 month old daughter tends to wiggle and squirm until she's half out of it. I really didn't like the Bjorn. I'm pretty large-chested, and and exclusively front-hold only worked when she was really little. I love my Ergo!