The following link will take you to the USSSA baseball site and the 2006 rules.
http://www.usssabaseball.org/content...y-laws2306.pdf
You should read these because there are significant limitations on the number of innings a player may pitch. Here in Northern California, pitching logs are kept, and signed by opposing coaches and one umpire after each game. It is unfortunately common to see a team disqualified for improperly using a pitcher.
For what it is worth, I watch a lot of USSSA games, usually featuring one of my sons, and I have never seen a pitcher return to the mound after being pulled. In Southern California, the rules explicitly state that a pitcher may not return.
http://www.baseballfirst.com/rules2.htm