Camo Quilt Project - http://camoquiltproject.blogspot.com/
Camo quilts are made from the same camouflage material as the soldiers' uniforms and are sent to military troops serving in Iraq and Afghanistan.
Operation Kid Comfort - http://www.asymca.org/what-we-do-3/national-programs-services/operation-kid-comfort/
Operation Kid Comfort is a project of the Armed Services YMCA. Volunteers assemble quilts for the young children of deployed military members. The quilts are made with photos of family to ease the grief of separation.
Operation Support for Deployed Military - http://www.operationsupportfordeployedmilitary.org/index.php"
Sewing angels make pillowcases and Christmas stockings for military personnel serving overseas. They also make cuddle quilts for babies born to service members of an adopted unit during their deployment.
Patriotic Pillow Project - http://patrioticpillowproject.org/
Volunteers can make these small pillows that resemble an American flag and mail them to the organizer for distribution to wounded service members.
Quilts of Valor - http://qovf.org/
The mission of Quilts of Valor is "to cover each of our service members and veterans wounded or touched by war with a comforting Quilt of Valor." Make a quilt for a service member/veteran or donate fabric. They also need longarm quilters.
Sew Much Comfort - http://sewmuchcomfort.org/index.asp
Volunteers make adaptive clothing for wounded service members and provide it free of charge to the recipients.
Soldiers' Angels - http://www.soldiersangels.org/
Soldiers' Angels provides support and care packages to military service members and their families in various ways. There is a dedicated sewing team that has several different types of sewing related projects.
I hope that this list helps you find an organization for which you can sew items. If you know of other organizations needing sewing assistance, whether local or national, please let me know and I will update the list.