Carrying the baby around teaches the baby the rhythm of your movements. It also helps your baby to strengthen his muscles when you bend down or reach up and the gravity pulls the baby onto a different position.
Carrying helps the baby's critical thinking skills. He observes how you perform your tasks from a very unique point. This observation creates impressions and memories for the child to build on his thinking skills.
The carriers bellow are the ones I recommend. They keep the baby safe, steady and just as important, they are the best for the parents, saving their backs from the extra work.