Check out the post on Avinash Kaushik’s Occam’s Razor blog about measuring the offline impact of online marketing.  Avinash is a past (and hopefully future) speaker at Shop.org and highly regarded as one of the world’s foremost experts on Web analytics.  He offers some great tips on this post.  If I can use Avinash’s language, the post is “awesomely cool” and very relevant to multichannel retailers.  Enjoy!