Bruderhof Communities in the UK - communitarian Anabaptist groups
Church Net UK - extensive list of churches, Christian organisations and resources
CTBI - Churches Together in Britain and Ireland
Ekklesia - not-for-profit think-tank which works to promote theological ideas in the public square
Greenbelt Festival - UK Christian arts festival
Iona Community - ecumenical Christian community
emphasising spirituality, peace and justice
Leaving M√ľnster - a mini-portal to a number of Resources on following Jesus in a post-christendom world (including a blog recording lessons learned and mistakes made along the way).
Living Word Library - London based guide to Christian web resources
London Mennonite Centre - rooted in the Anabaptist tradition, cultivating Christian discipleship as a way of life:

New Way of Being Church - creating processes for transformation in church and world
Simon Barrow - Theology and More... - Secretary of CCOM and Assistant General Secretary of CTBI - links to Simon's writings on issues of theology and society, religion and current affairs, and to related organisations

UK Christian Handbook - online version of UK Christian directory
Wood Green Mennonite Church - Mennonite Church in London
Anabaptist Studies - Lloyd Pietersen's Anabaptist studies blog
Workshop - national leadership and discipleship training programme