Find Mission Opportunities
ShortTermMissions.com helps people quickly connect with short-term mission trips that fit their gifts, calling, and availability, listing hundreds of mission trip provided by many agencies.
Mission Finder lists hundreds of short term, medical, domestic, and international mission trips, categorized by location and type of ministry. Lots of links, short descriptions.
ChristianJobs.com is not specifically focused on missions opportunities, but lists options for employment at ministry organizations, nonprofits, and Christian businesses.
If you want an opportunity offered by a mission organization in another country, try OSCAR (UK and Europe).
Don't forget that some mission agencies list specific opportunities right on their websites. Others would be happy to tell you about specific ways to serve with them if you contact them by phone or email. Ask mission agencies about short-term and long-term opportunities. Don't overlook what are sometimes called "mid-term" opportunities, those which last for from several months up to a year or two. Sometimes these are not advertised, but they may provide the best way to get to know an agency while being further equipped for a lifetime of ministry.