{% for category in craft.categories.group('resourceCategories') %}
  {% set entryCount = craft.entries.relatedTo(category).total() %}
  ... do something...
{% endfor %}

{% set resourceEntries = craft.entries(queryParams).section('and, not organizations, not presentersAndAuthors') %}
 {% set entryCount = resourceEntries.relatedTo(category).total() %}
  ... do something...
{% endfor %}