Best soft cotton fabrics for apparel?

I've done a lot of apparel sewing in the last year and my biggest issue is finding cotton (not quilter's cotton!) light-weight enough to make nice apparel. I find a lot to be very stiff and makes things look boxy. for the most part I've gotten away with this by using flannel or sheets from the goodwill.

What are you favorite fabrics (either type, website, or even specific fabric) that you like to use for a cotton top, dress, thin skirt, etc?