As you may or may not know, Little League has banned the use of composite bats, pending testing. There have been some bats that have received a waiver clearance (permitting them to be used).
If you play at the Majors level (2 1/4" bats), and you don't see your bat among the ones displayed below, your bat has not received clearance.
These are the approved bats as of March 30, 2011.
To find out more or to see which bats have been approved at other levels, please follow the link below: Little League Bat Info.