My all time favorite recommendations are the Adjustable Fleece Pouches, from Kangaroo Korner, and the Zolowear slings (either cotton or silk, they're both fab).
I use both, love them both, and for all the overdoing of the collection that I've done, I'd be a happy woman as long as I had one of each. In my opinion, the fleece pouch is perfect for an up and down toddler, and it's so snuggly, though it may be a little warm in summer. I can wear it on lower humidity days in the summer, but it is a dream fall through early summer.
The Zolos are just such a smart design, shoulderwise, that they are just terrific and easy to wear. I can sling my 14 month old just as easily as my 3 year old in it, with minimal adjustment.
I think it's just a matter of what kind of sling/carrier you want, but in my never to humble opinion a KK AFP or a Zolo, and you'll be good to go!
If you have more specific question, feel free to pick my brain. Let's use this addiction for good, not evil.....