the babyhawk is the best! (www.babyhawk.com) it's much better than the Ergo, lighter, easy to put on, you can wear it on your front or back. it folds small so you can stick it in a diaper bag. it doesn't have buckles, just ties, so you don't need to adjust any "settings" for different size adults wearing it. it's from newborn to 40lbs. i've used it extensively with my daughter, now it sits in the closet as i'm pregnant, but I plan to use it even more with #2, once she is born in Oct :)
If you are looking for a sideways sling, the slingling is pretty good too. the one thing I don't like about it, is that it hangs on your shoulder, so you are not really able to lift that arm up and down too much, that's why i prefer the carrier. Slinglings are on mamabargains.com sometimes for 60%, you just have to watch for them.
good luck!