Below are several mission-sending agencies of which I have some knowledge, either directly or through missionary friends. In addition to exploring these missions directly, feel free to contact me as to why I think they may or may not be a good match for your interests.
Global Teams - Working in unreached Muslim, Animist, Hindu and Buddhist countries with teams composed of people from various countries
Studio TEN - Working through local churches with at-risk children & women in Nepal
Back2Back Ministries - Caring for orphans and at-risk children in cooperation with missionaries, local churches and international sponsors
Christ for the City International - Transforming cities through local missional bases
Latin America Mission - Placing missionaries throughout Latin America
Commission to Every Nation - Helping ordinary people go out as missionaries
SIM - Helping churches and missionaries establish cross-cultural ministries
SEND International - Mobilizing missionaries and planting churches
Cornerstone International - Prayer, worship, and mobilizing missionaries
Cru - Reaching people for Christ in university settings (formerly known as Campus Crusade)
One Mission Society - Partners with many organizations and denominations to spread the gospel worldwide
Youth With A Mission - Missions for post-high school students combining discipleship training with outreach.
The following are several mission resources that I have found helpful.
Evangelical Missions Quarterly - EMQ is the premier mission journal for professional missionaries. It is geared to the practicing professional, not the ivory tower missiologist
Mission Frontiers - An easy read on contemporary mission issues
International Journal of Frontier Missions - Focusing especially on the least-reached segment of the world. The articles are more scholarly and at times controversial (at least within the small circle that follows the particular issues)
International Bulletin of Missionary Research - Christian mission history and analysis from a scholarly perspective
Missiology: An International Review - Scholarly journal of missions studies and practical anthropology
William Carey Library - A great source for mission-related books that you simply will not find at Christian bookstores geared to mono-cultural Christians
Urbana - Intervarsity’s Urbana tri-annual missions conferences are an excellent way to expose college students to the challenges and possibilities of missionary service
These are some of the schools providing quality missionary training.
Asbury Theological Seminary - Located in Kentucky, Asbury offers both masters and doctoral level training in missions
Fuller Theological Seminary - Located in southern California, Fuller has been a forerunner in missions / intercultural training for decades
Bethel College - Located in northern Indiana offers solid undergrad training in intercultural studies
Wheaton College - Located in Chicago, Wheaton has a long tradition of raising up missionaries from its undergraduate programs, as well as serving many missionary kids