This book, Serving as Senders, gives lots of excellent ideas on how to help missionaries.

Pray for them, encourage them in their work; one could give to their ministry, but don’t overwhelm them with too many emails. (smile)
Propempo has developed organized ways you can help missionaries through advocacy, encouraging, and providing expertise in ten different areas. See below.
Contact us for training at your church!
Take the Church Missions Profile to get recommendations about developing ways to support them!

Ten areas of Barnabas Team support, first six taken from Pirolo's book:
* Moral support
* Logistics support
* Financial support
* Prayer support
* Communication support
* Re-entry support
* Children's education
* Security & contingency
* Technology
* Field visits & short term missions teams/projects