This codeplex project allows developers to package list lookup columns as a feature and as part of a content type.  This gets us around a challenge where developers try to deploy a content type that has a list lookup column which is dependent on a list instance.

http://fieldlookupbuilder.codeplex.com/

It extends the work done by Chris O’Brien that made list lookup columns as a feature.

SharePoint 2007 - create lookup fields as a feature