CCK checkboxes with no labels
you can use visibility:hidden; (and height and/or width 0px). I use visibility:hidden; when display:none is not useful (issues of inheritances of CSS, or maybe still you can need the values of the hidden elements).

Other suggestion. I have several forms that use lots of checkboxes, so I use Vertical Tabs http://drupal.org/project/vertical_tabs to divide the forms in several tabs, to show only one group of checkboxes per tab. So here is not necessary to remove labels of checkboxes.