Jo-Ann Sensations Beautiful Yarn : yarn : knit & crochet : Shop | Joann.com
This yarn is nice and soft. I would do it on size 12 needles, even though it recommends 10.5. I usually like to use larger needles than what's recommended.
Patons Melody Yarn : yarn : knit & crochet : Shop | Joann.com
I also love this yarn. Again, I'd use size 13 needles instead.
Lion Brand Vanna's Choice Yarn : yarn : knit & crochet : Shop | Joann.com
These yarns are also nice and soft. You'd need smaller needles than the ones above. I like to use 11 needles for this one.
These are just some of my favorite yarns. It's really best if you can go to a store with yarn (joanns or michael's usually have really good selections. Or if there's a more local yarn shop, they're usually more helpful). And I'd recommend looking for thicker yarns, and using larger needles. They'll knit up faster and still look nice with the simple stitches.