One word of caution. Some missionaries are in closed countries, e.g. countries that don't welcome missionaries. Find out what communication guidelines are suggested before you send something. The Missions Team can help you learn the appropriate guidelines. Material Support Provide for their finance support.
Most missionaries are under-supported.
Think about committing to give a regular amount to the a missionary. Help meet special or unexpected needs such as medical care, transportation, equipment, or special projects. Offer to fly them back for a retreat or vacation. Send holiday and care packages containing money or needed items. Find out what favorite foodstuffs, healthcare products, or other supplies are not available in their country and send them periodically.