Make your own sling
If you have, or are willing to develop even the most basic sewing skills, you can make your own sling. This will save you money, and allow you to choose the fabric, size, and level of padding that suits you best.
Nearly comprehensive sling/carrier sewing list: http://www.thebabywearer.com/lists/Sewing.htm
There are now a number of great instructions online for using rings and a scarf or similar item to make a sling without sewing.
An onbuhimo (or onbu for short) is a Japanese back carrier. It uses a small rectangle, 2 long straps and 2 loops or rings to make a back pack shape for carrying a child. Depending on construction and technique it can be used for babies of many ages, carried on the front or the back of the parent. There is a crafty and simple tutorial at Placemat onbuhimo tutorial
You can find sling sewing tips and helps, and lots of positive feedback at these interactive forums. You will need to join to participate, but it's worth it! You may even find one of our elusive coupons.
Once you have examined a sling or a sling pattern you will see that with a little experimentation you can have the sling that's ideal for you.