Flax by Tin Can Knits is a perfect first sweater project! It's knit seamlessly from the collar to the cuffs.
The pattern includes 7 child and 10 adult sizes (isn't that great?) and calls for a worsted weight yarn.
It's knit using sizes US 6 and 8 needles.
ImagiKnitter Amanda is making one using Cotton Merino. Check it out here.
This pattern is available as a PDF download.