Chuck,
Some would say that ASA is to softball what Little League is to baseball. Basically it's one of the, if not the, largest sponsor of "recreational" softball in the country. They have leagues from 8yo up to adult. Many of the HS girls play on a 16U or 18U team in the summer and fall. I've put a link to their website below if you are interested.
While there are still a number of differences between FED softball and ASA softball, the NFHS rules committee took some major strides this year to bring the rules closer together (e.g. the new appeal and obstruction rules). So calling ASA ball in the summer and fall is a good way to gather experience for FED ball.
ASA Softball