The Bible and the Prayer Book are the foremost resources. Most worship leaders gather up some supplementary resources. A high priority for many is a book of prayers and related materials for use in services to supplement the Prayer Book. A recent book of resources worth adding to your collection is:
Timothy Radcliffe (ed.) Just One Year: Prayer and Worship through the Christian Year, London: Darton, Longman and Todd (2006). ISBN – 10:0-232-52669-9. ISBN – 13:978-0-232-52669-1.
Apart from resources for use in composing services, this book is worth a look because of two introductory chapters:
‘The Christian Year: What Does It Mean To Celebrate It?’
‘Practical Advice in Creating a Liturgy’