Devel module and Krumo
Sometimes, if I need to differentiate between different debug items, I'll use something like the following:

kpr(array(
  'node' =&gt; $node,
  'comments' =&gt; $comments,
  'links' =&gt; $links,
));


Or, if debug items are split in different places, just simply:

kpr(array('user' =&gt; $user));