One of the things you can do in SharePoint 2010 is pull multiple data elements through from a list as part of a look up. Say you have a list which contains projects and records project name, project manager, project sponsor &c. In a 2007 lookup field you can pull through one element only so you can have project name OR project manager OR project sponsor, but not two or more of them. In 2010 it is possible to have a look up that will pull through multiple elements. E.G. you select the project name and it will pull through the corresponding project manager data.
To achieve this in SharePoint 2007 you need to create a workflow and use the 'set' functionality to query the data and insert it intot he appropriate field for each element.