From the Zionist Federation:

Israeli soldier Gilad Shalit has been held captive in Gaza since June 2006.  The Zionist Federation is supporting efforts this month to raise awareness of his plight and to secure his release.

One idea is to send Rosh Hashanah cards to Gilad.  The Jewish New Year begins in late September and the Zionist Federation encourages you to send your wishes and prayers to Gilad.  Cards are being solicited from around the world and will be presented to Gilad's father for delivery to the Red Cross in Israel, with the hope that they can be delivered personally to Gilad in captivity.  We have also arranged a meeting with British Red Cross officials in London to raise the issue of Gilad's detention.

Website link: Send Gilad Your New Year Greeting