The link for all of the girls national tournaments is here. This is both National Championships and the National Invitation Championships (AAU equivalent of NIT!). Regardless of which tournament, it is always a high level of play. These tournaments are scattered around the country, as you will see fom the website.
http://www.aaugirlsbasketball.org/pa...urnaments.html
The boys information may be found at:
http://www.aauboysbasketball.org/
The boys tournaments appear to be mainly in Florida and Tennessee.