I think I'd put Nynaeve in Ravenclaw. Despite her temper she's not crazy-reckless (call me prejudiced but that's the trait I associate with Gryffindors) and she tries to learn all she can about herbs and healing.

Elayne is definitely a Gryffindor and so is Moiraine.

Egwene goes straight into Slytherin.

Mat is a Gryffindor who thinks he should be a Slytherin and keeps griping about how he's not really brave.

Rand is hard to sort. He doesn't embody any of the distinctive traits of each house. I might put him in Hufflepuff, for sheer stubbornness and grit.

If you want Ajah parallels, Red and Green map to Gryffindor, Brown and White to Ravenclaw, Yellow and Gray to Hufflepuff and Blue and Black to Slytherin.