Title to Category ID(s)
September 30, 2011 | ExpressionEngine
Url title to cat_id
Example usage:
{exp:channel:entries channel="news"}
{exp:title_cat url_title="{url_title}" separator="&"}
{/exp:channel:entries}
This would return something like: 1&2&3
It can be used outside of the exp:channel:entries tag as well.