Two of my favorites that are pretty verstile are Asian Carriers and wraps.
An asian carrier is a square of fabric with 4 straps the you tie the carrier onto you with. Very adjustable and can be worn on the front or back. the most well known is the Kozy but more can be found at
www.TheBabyWearer.com .
Wraps come in a variety. Wraps are a long piece of fabric used to tie the babe too you. They can be tricky at first but after you get the hang of tying its a piece of cake. My fave is the Moby Wrap for front carries. Its also slightly stretchy and you can put this one on without the baby first.
I have also perfected cayying my kiddo on my back in a regular ring sling. I started when she was quite little. The trick is to get a sling thats really adjustable so you can snug them up tight but one thats wide enough so theres lots of fabric holding them in. I use The Baby Space AP and a Silk Zolo for back carries most of the time.
Goodluck!