Here are some websites that may interest you:

The Billy Graham Evangelistic Association (BGEA)
http://www.bgea.org/

Evangelical Alliance (EA)
http://www.eauk.org/

Summer Madness
http://www.summermadness.co.uk/

Exodus
http://www.exodusonline.org.uk/

Youth For Christ Northern Ireland (YFCNI)
http://www.yfcni.org/

Girls Brigade Northern Ireland (GBNI)
http://www.gbni.co.uk/

IFES Ireland
http://www.ifesireland.org/index.php

Crown Jesus
http://www.crownjesus.org/

Samaritan's Purse
http://www.samaritanspurse.uk.com/index.asp

Evangelical Ministries
http://www.emins.com/Home.aspx?area=20

Grow In Grace
http://www.growingrace.org/