I just found this.
This link has some concert band contests and such:
ASCAP Composition Opportunities
This should be a real good one:
(You have to be 18 however.)
ASCAP/CBDNA Frederick Fennell Prize for
The Best Original Score for Concert Band
Program Administered by ASCAP's Concert Music Department
ASCAP and the College Band Directors National Association (CBDNA) seek to recognize talented young composers who write music for Concert Band. The prize is $5,000. The ASCAP/CBDNA Frederick Fennell prize is awarded bi-annually. The winning score will be performed at the 2007 CBDNA Conference.
Applicants must be citizens or permanent residents of the United States of America, or enrolled students with student visas who have not reached their 30th Birthday by January 1, 2007.
How to apply: Open to citizens or permanent U.S. residents, or enrolled students with student visas, who are between the ages of 18 and 30 as of January 1, 2007.
Deadline: All applications must be postmarked no later than September 15, 2006.