I think the freebie I've used most is probably a light set from Wax Productions (the site has gone now) - this set is used in almost all of the recent freebie previews on my site, which is the only rendering I seem to do nowadays.

A close second would probably be Vali's Mayte texture for V3 (who also seems to have disappeared), which is used in a slightly modified form on my "default" V3 model. Her hair is usually my own Flo Hair, but I hesitate to blow my own trumpet to such an extent. ;)