One of the recent trends in fundraising has been the sale of rubber wristbands that feature a slogan or other catchphrase of the organization your purchase supports. Originally made popular by the Lance Armstrong Foundation's yellow LIVESTRONG wristbands, your purchase of the band supports the charity, and you can literally wear your support on your sleeve.
People "in the know" will know that you support the cause and curious onlookers may ask about the band, giving you an opportunity to share information and raise awareness about the cause. One word of caution about charity wristbands: due to their recent popularity, there has emerged a re-selling market. If you buy a wristband from a re-seller, you not only might pay more for it, but the money is most likely not being directed to the charity the wristband was developed to support.
*Make sure you buy from an authorized source so that the charity gets the benefit.