Benjamin Smiles - http://www.friendsandco.net/benjamin/benamin-smiles.html
Volunteers make travel size pillowcases for children suffering from cancer. Pillows can be given to a local Ronald McDonald House or pediatric hospital. You can also send pillowcases to the organizer for distribution.
Brimming with Love - http://www.brimmingwithlove.org/
Brimming with Love's mission is to provide new and hand-made hats to hospitals in the Dallas-Ft. Worth Metroplex area to be distributed free of charge to men and women undergoing treatment for cancer. There are several sewn hat patterns available.
ConKerr Cancer - http://conkerrcancer.org/
The brightly colored pillowcases that the ConKerr Cancer volunteers make for children ill with cancer brighten and cheer up the sterile hospital rooms. There are many ways to use your sewing skills to help.
Head Huggers - http://www.headhuggers.org/
Hair loss is just one of the icky side effects of chemotherapy. Through Head Huggers, you can help provide comfort to someone suffering from hair loss. Many patterns are provided.
Heart Pillow Project - http://www.heartpillow.dk/
This organization makes heart shaped pillows to ease pain after breast cancer surgeries. Contact the organizer to see how you can help.
Multiple Sclerosis Quilt Project - http://msquiltprojectabout.blogspot.com/
Help raise awareness of Multiple Sclerosis by submitting a quilt panel to be made into a larger quilt to honor of those affected by MS.
Operation Alzheimers Prevention - http://www.sewnews.com/articles/SewSupport
Sew News has partnered up with the Mountain State Division of Life Care Centers of America to raised money in support of the Alzheimer's Association. They are requesting completed quilts that will be auctioned. They provide a free quilt pattern or you can use the pattern of your choice.
Quilters Against Breast Cancer - http://www.makingmemories.org/quilt.html
Quilters make quilts out of donated wedding gowns to be used in a traveling exhibit or sold to raise funds for granting final wishes for terminal breast cancer patients. After requesting a kit, gowns will be sent to you.
Sewn in Love - http://www.sewn-n-love.org/wordpress/index.php
Sewn in Love volunteers make, collect, and donate quilts to cancer patients of all ages. The finished quilts are distributed to cancer treatment centers, hospitals and cancer support groups.
Stitching for Pink - http://www.victoriasquilts.com/
Victoria's Quilt volunteers make and donate handmade quilts to cancer patients and cancer treatment centers.
Wild Ginger iCare - http://www.wildginger.com/icare/
Wild Ginger, the makers of pattern making software, has created a special line of patterns that are free to use for making gowns, pajamas, and accessories for medical patient care. The patterns are sizable allowing customization.
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.