The monograph Missing data in clinical trials - a practical guide by James Carpenter and Mike Kenward has been published by the National Health Service's National Co-ordinating Centre for Research Methodology, and is available for download here.
Please cite this as
Carpenter, J. R. and Kenward M. G. (2008) Missing data in randomised controlled trials - a practical guide. Birmingham: National Institute for Health Research, Publication RM03/JH17/MK. Available at http://www.missingdata.org.uk