While doing research and shopping for an installation in an upcoming show, I wanted to find a yarn store that wasn't too expensive yet had a spectrum of colors and variety. Also, one where I didn't have to trek out to Queens or Staten Island to go to a Michael's or JoAnn's. Right on 15th Street between 5th and 6th Ave is the Lion Brand Yarn Studio. The variety of yarns and colors are great, in addition to there being a weekly crocheting and knitting doctor (who I will need to make an appointment with).
Here, they have every variety of yarn they carry so that you can take a swatch and knit/crochet before you purchase so you know how it will look.