Dynamic Logic have just released their latest study:

Dynamic Logic, a Millward Brown company, releases new analysis of 32 cross-media campaigns across ten categories showing that media work best when used together. All three media platforms – television, magazines, and online – contribute incrementally to brand metrics, but at different levels, bringing various strengths at different points along the purchase funnel. TV and online’s contributions were more apparent during the awareness stages while magazines were stronger at building brand favorability and purchase intent.

Check it out: http://www.dynamiclogic.com/na/research/WhatsInTheMix/Oct2007.html