hm... you can soften cotton by putting it in a bucket with fabric softener and leaving it in there overnight.
warning though. fabric softeners actually break down the fibers, so the fabric will not actually become SOFTER at the thickness it is at, but rather will become fluffier, giving the illusion of softness, but is actually just ripping the fibers apart, ending up with a thinner material that is more loosely woven.
btw, this is the problem I am noticing with the thin knit tops now.. (ie C&C) its why they like... get holes like no tommorrow.