I've made some slings, mei tai's, wraps, and soft structured carriers. My favorite carrier for nursing is a sling. For carrying an infant I liked a wrap. For a larger infant a mei tai (Asian Style baby carrier) in a front carry, and for a toddler a soft structured carrier in a back carry. Here are a few carriers I have made. I've made more but unfortunately I didn't always get picturees before I gave them away.
The best sites I have found to get help and free patterns for sewing is Jan Andrea's website. And thebabywearer.com's Do It Yourself Forum.
Specific free patterns that I have tried and liked:
Wrap - I used knit t-shirt fabric and just cut it and didn't sew anything.
Mei Tai (ABC) - I made one with this pattern and one with my own pattern and this was easier.
Sling - I've used a lightweight denim and knit t-shirt fabric and liked the knit one better but it doesn't work as well for older babies.
Soft Structured Carrier - The one I made in the pictures was my own pattern. I am in the process of making this one, but so far it looks better than my own pattern.
Wrap or SPOC (Simple Piece of Cloth)
Soft Structured Carrier
Mei Tai or ABC (Asian Baby Carrier)